Properly handle the mftb instruction.

The mftb instruction was incorrectly marked as deprecated in the PPC
Backend. Instead, it should not be treated as deprecated, but rather be
implemented using the mfspr instruction. A similar patch was put into GCC last
year. Details can be found at:

https://sourceware.org/ml/binutils/2014-11/msg00383.html.
This change will replace instances of the mftb instruction with the mfspr
instruction for all CPUs except 601 and pwr3. This will also be the default
behaviour.

Additional details can be found in:

https://llvm.org/bugs/show_bug.cgi?id=23680

Phabricator review: http://reviews.llvm.org/D10419

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239827 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp b/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
index 1736d03..a699a55 100644 (file)
--- a/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
+++ b/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
@@ -1184,6 +1184,13 @@ void PPCAsmParser::ProcessInstruction(MCInst &Inst,
     Inst = TmpInst;
     break;
   }
+  case PPC::MFTB: {
+    if (STI.getFeatureBits()[PPC::FeatureMFTB]) {
+      assert(Inst.getNumOperands() == 2 && "Expecting two operands");
+      Inst.setOpcode(PPC::MFSPR);
+    }
+    break;
+  }
   }
 }
 

diff --git a/lib/Target/PowerPC/PPC.td b/lib/Target/PowerPC/PPC.td
index 1a02bcc..641b237 100644 (file)
--- a/lib/Target/PowerPC/PPC.td
+++ b/lib/Target/PowerPC/PPC.td
@@ -135,9 +135,9 @@ def FeatureInvariantFunctionDescriptors :
                    "Assume function descriptors are invariant">;
 def FeatureHTM : SubtargetFeature<"htm", "HasHTM", "true",
                                   "Enable Hardware Transactional Memory instructions">;
+def FeatureMFTB   : SubtargetFeature<"", "FeatureMFTB", "true",
+                                        "Implement mftb using the mfspr instruction">;
 
-def DeprecatedMFTB   : SubtargetFeature<"", "DeprecatedMFTB", "true",
-                                        "Treat mftb as deprecated">;
 def DeprecatedDST    : SubtargetFeature<"", "DeprecatedDST", "true",
   "Treat vector data stream cache control instructions as deprecated">;
 
@@ -165,7 +165,7 @@ def ProcessorFeatures {
        FeaturePOPCNTD, FeatureCMPB, FeatureLDBRX,
        Feature64Bit /*, Feature64BitRegs */,
        FeatureBPERMD, FeatureExtDiv,
-       DeprecatedMFTB, DeprecatedDST];
+       FeatureMFTB, DeprecatedDST];
   list<SubtargetFeature> Power8SpecificFeatures =
       [DirectivePwr8, FeatureP8Altivec, FeatureP8Vector, FeatureP8Crypto,
        FeatureHTM, FeatureDirectMove, FeatureICBT, FeaturePartwordAtomic];
@@ -247,61 +247,75 @@ include "PPCInstrInfo.td"
 // PowerPC processors supported.
 //
 
-def : Processor<"generic", G3Itineraries, [Directive32]>;
+def : Processor<"generic", G3Itineraries, [Directive32, FeatureMFTB]>;
 def : ProcessorModel<"440", PPC440Model, [Directive440, FeatureISEL,
                                           FeatureFRES, FeatureFRSQRTE,
                                           FeatureICBT, FeatureBookE, 
-                                          FeatureMSYNC, DeprecatedMFTB]>;
+                                          FeatureMSYNC, FeatureMFTB]>;
 def : ProcessorModel<"450", PPC440Model, [Directive440, FeatureISEL,
                                           FeatureFRES, FeatureFRSQRTE,
                                           FeatureICBT, FeatureBookE, 
-                                          FeatureMSYNC, DeprecatedMFTB]>;
+                                          FeatureMSYNC, FeatureMFTB]>;
 def : Processor<"601", G3Itineraries, [Directive601]>;
-def : Processor<"602", G3Itineraries, [Directive602]>;
+def : Processor<"602", G3Itineraries, [Directive602,
+                                       FeatureMFTB]>;
 def : Processor<"603", G3Itineraries, [Directive603,
-                                       FeatureFRES, FeatureFRSQRTE]>;
+                                       FeatureFRES, FeatureFRSQRTE,
+                                       FeatureMFTB]>;
 def : Processor<"603e", G3Itineraries, [Directive603,
-                                        FeatureFRES, FeatureFRSQRTE]>;
+                                        FeatureFRES, FeatureFRSQRTE,
+                                        FeatureMFTB]>;
 def : Processor<"603ev", G3Itineraries, [Directive603,
-                                         FeatureFRES, FeatureFRSQRTE]>;
+                                         FeatureFRES, FeatureFRSQRTE,
+                                         FeatureMFTB]>;
 def : Processor<"604", G3Itineraries, [Directive604,
-                                       FeatureFRES, FeatureFRSQRTE]>;
+                                       FeatureFRES, FeatureFRSQRTE,
+                                       FeatureMFTB]>;
 def : Processor<"604e", G3Itineraries, [Directive604,
-                                        FeatureFRES, FeatureFRSQRTE]>;
+                                        FeatureFRES, FeatureFRSQRTE,
+                                        FeatureMFTB]>;
 def : Processor<"620", G3Itineraries, [Directive620,
-                                       FeatureFRES, FeatureFRSQRTE]>;
+                                       FeatureFRES, FeatureFRSQRTE,
+                                       FeatureMFTB]>;
 def : Processor<"750", G4Itineraries, [Directive750,
-                                       FeatureFRES, FeatureFRSQRTE]>;
+                                       FeatureFRES, FeatureFRSQRTE,
+                                       FeatureMFTB]>;
 def : Processor<"g3", G3Itineraries, [Directive750,
-                                      FeatureFRES, FeatureFRSQRTE]>;
+                                      FeatureFRES, FeatureFRSQRTE,
+                                      FeatureMFTB]>;
 def : Processor<"7400", G4Itineraries, [Directive7400, FeatureAltivec,
-                                        FeatureFRES, FeatureFRSQRTE]>;
+                                        FeatureFRES, FeatureFRSQRTE,
+                                        FeatureMFTB]>;
 def : Processor<"g4", G4Itineraries, [Directive7400, FeatureAltivec,
-                                      FeatureFRES, FeatureFRSQRTE]>;
+                                      FeatureFRES, FeatureFRSQRTE,
+                                      FeatureMFTB]>;
 def : Processor<"7450", G4PlusItineraries, [Directive7400, FeatureAltivec,
-                                            FeatureFRES, FeatureFRSQRTE]>;
+                                            FeatureFRES, FeatureFRSQRTE,
+                                            FeatureMFTB]>;
 def : Processor<"g4+", G4PlusItineraries, [Directive7400, FeatureAltivec,
-                                           FeatureFRES, FeatureFRSQRTE]>;
+                                           FeatureFRES, FeatureFRSQRTE, 
+                                           FeatureMFTB]>;
 
 def : ProcessorModel<"970", G5Model,
                   [Directive970, FeatureAltivec,
                    FeatureMFOCRF, FeatureFSqrt,
                    FeatureFRES, FeatureFRSQRTE, FeatureSTFIWX,
-                   Feature64Bit /*, Feature64BitRegs */]>;
+                   Feature64Bit /*, Feature64BitRegs */,
+                   FeatureMFTB]>;
 def : ProcessorModel<"g5", G5Model,
                   [Directive970, FeatureAltivec,
                    FeatureMFOCRF, FeatureFSqrt, FeatureSTFIWX,
                    FeatureFRES, FeatureFRSQRTE,
                    Feature64Bit /*, Feature64BitRegs */,
-                   DeprecatedMFTB, DeprecatedDST]>;
+                   FeatureMFTB, DeprecatedDST]>;
 def : ProcessorModel<"e500mc", PPCE500mcModel,
                   [DirectiveE500mc, FeatureMFOCRF,
                    FeatureSTFIWX, FeatureICBT, FeatureBookE, 
-                   FeatureISEL, DeprecatedMFTB]>;
+                   FeatureISEL, FeatureMFTB]>;
 def : ProcessorModel<"e5500", PPCE5500Model,
                   [DirectiveE5500, FeatureMFOCRF, Feature64Bit,
                    FeatureSTFIWX, FeatureICBT, FeatureBookE, 
-                   FeatureISEL, DeprecatedMFTB]>;
+                   FeatureISEL, FeatureMFTB]>;
 def : ProcessorModel<"a2", PPCA2Model,
                   [DirectiveA2, FeatureICBT, FeatureBookE, FeatureMFOCRF,
                    FeatureFCPSGN, FeatureFSqrt, FeatureFRE, FeatureFRES,
@@ -309,7 +323,7 @@ def : ProcessorModel<"a2", PPCA2Model,
                    FeatureSTFIWX, FeatureLFIWAX,
                    FeatureFPRND, FeatureFPCVT, FeatureISEL,
                    FeaturePOPCNTD, FeatureCMPB, FeatureLDBRX, Feature64Bit
-               /*, Feature64BitRegs */, DeprecatedMFTB]>;
+               /*, Feature64BitRegs */, FeatureMFTB]>;
 def : ProcessorModel<"a2q", PPCA2Model,
                   [DirectiveA2, FeatureICBT, FeatureBookE, FeatureMFOCRF,
                    FeatureFCPSGN, FeatureFSqrt, FeatureFRE, FeatureFRES,
@@ -317,7 +331,7 @@ def : ProcessorModel<"a2q", PPCA2Model,
                    FeatureSTFIWX, FeatureLFIWAX,
                    FeatureFPRND, FeatureFPCVT, FeatureISEL,
                    FeaturePOPCNTD, FeatureCMPB, FeatureLDBRX, Feature64Bit
-               /*, Feature64BitRegs */, FeatureQPX, DeprecatedMFTB]>;
+               /*, Feature64BitRegs */, FeatureQPX, FeatureMFTB]>;
 def : ProcessorModel<"pwr3", G5Model,
                   [DirectivePwr3, FeatureAltivec,
                    FeatureFRES, FeatureFRSQRTE, FeatureMFOCRF,
@@ -325,41 +339,42 @@ def : ProcessorModel<"pwr3", G5Model,
 def : ProcessorModel<"pwr4", G5Model,
                   [DirectivePwr4, FeatureAltivec, FeatureMFOCRF,
                    FeatureFSqrt, FeatureFRES, FeatureFRSQRTE,
-                   FeatureSTFIWX, Feature64Bit]>;
+                   FeatureSTFIWX, Feature64Bit, FeatureMFTB]>;
 def : ProcessorModel<"pwr5", G5Model,
                   [DirectivePwr5, FeatureAltivec, FeatureMFOCRF,
                    FeatureFSqrt, FeatureFRE, FeatureFRES,
                    FeatureFRSQRTE, FeatureFRSQRTES,
                    FeatureSTFIWX, Feature64Bit,
-                   DeprecatedMFTB, DeprecatedDST]>;
+                   FeatureMFTB, DeprecatedDST]>;
 def : ProcessorModel<"pwr5x", G5Model,
                   [DirectivePwr5x, FeatureAltivec, FeatureMFOCRF,
                    FeatureFSqrt, FeatureFRE, FeatureFRES,
                    FeatureFRSQRTE, FeatureFRSQRTES,
                    FeatureSTFIWX, FeatureFPRND, Feature64Bit,
-                   DeprecatedMFTB, DeprecatedDST]>;
+                   FeatureMFTB, DeprecatedDST]>;
 def : ProcessorModel<"pwr6", G5Model,
                   [DirectivePwr6, FeatureAltivec,
                    FeatureMFOCRF, FeatureFCPSGN, FeatureFSqrt, FeatureFRE,
                    FeatureFRES, FeatureFRSQRTE, FeatureFRSQRTES,
                    FeatureRecipPrec, FeatureSTFIWX, FeatureLFIWAX, FeatureCMPB,
                    FeatureFPRND, Feature64Bit /*, Feature64BitRegs */,
-                   DeprecatedMFTB, DeprecatedDST]>;
+                   FeatureMFTB, DeprecatedDST]>;
 def : ProcessorModel<"pwr6x", G5Model,
                   [DirectivePwr5x, FeatureAltivec, FeatureMFOCRF,
                    FeatureFCPSGN, FeatureFSqrt, FeatureFRE, FeatureFRES,
                    FeatureFRSQRTE, FeatureFRSQRTES, FeatureRecipPrec,
                    FeatureSTFIWX, FeatureLFIWAX, FeatureCMPB,
                    FeatureFPRND, Feature64Bit,
-                   DeprecatedMFTB, DeprecatedDST]>;
+                   FeatureMFTB, DeprecatedDST]>;
 def : ProcessorModel<"pwr7", P7Model, ProcessorFeatures.Power7FeatureList>;
 def : ProcessorModel<"pwr8", P8Model, ProcessorFeatures.Power8FeatureList>;
-def : Processor<"ppc", G3Itineraries, [Directive32]>;
+def : Processor<"ppc", G3Itineraries, [Directive32, FeatureMFTB]>;
 def : ProcessorModel<"ppc64", G5Model,
                   [Directive64, FeatureAltivec,
                    FeatureMFOCRF, FeatureFSqrt, FeatureFRES,
                    FeatureFRSQRTE, FeatureSTFIWX,
-                   Feature64Bit /*, Feature64BitRegs */]>;
+                   Feature64Bit /*, Feature64BitRegs */,
+                   FeatureMFTB]>;
 def : ProcessorModel<"ppc64le", P8Model, ProcessorFeatures.Power8FeatureList>;
 
 //===----------------------------------------------------------------------===//

diff --git a/lib/Target/PowerPC/PPCInstrInfo.td b/lib/Target/PowerPC/PPCInstrInfo.td
index c5a044c..b50124d 100644 (file)
--- a/lib/Target/PowerPC/PPCInstrInfo.td
+++ b/lib/Target/PowerPC/PPCInstrInfo.td
@@ -2225,7 +2225,7 @@ def MTSPR : XFXForm_1<31, 467, (outs), (ins i32imm:$SPR, gprc:$RT),
                       "mtspr $SPR, $RT", IIC_SprMTSPR>;
 
 def MFTB : XFXForm_1<31, 371, (outs gprc:$RT), (ins i32imm:$SPR),
-                     "mftb $RT, $SPR", IIC_SprMFTB>, Deprecated<DeprecatedMFTB>;
+                     "mftb $RT, $SPR", IIC_SprMFTB>;
 
 // A pseudo-instruction used to implement the read of the 64-bit cycle counter
 // on a 32-bit target.

diff --git a/lib/Target/PowerPC/PPCSubtarget.cpp b/lib/Target/PowerPC/PPCSubtarget.cpp
index a8ff4e1..cf603fe 100644 (file)
--- a/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -91,7 +91,7 @@ void PPCSubtarget::initializeEnvironment() {
   IsPPC4xx = false;
   IsPPC6xx = false;
   IsE500 = false;
-  DeprecatedMFTB = false;
+  FeatureMFTB = false;
   DeprecatedDST = false;
   HasLazyResolverStubs = false;
   HasICBT = false;

diff --git a/lib/Target/PowerPC/PPCSubtarget.h b/lib/Target/PowerPC/PPCSubtarget.h
index ee89a6e..e9cc3d4 100644 (file)
--- a/lib/Target/PowerPC/PPCSubtarget.h
+++ b/lib/Target/PowerPC/PPCSubtarget.h
@@ -110,7 +110,7 @@ protected:
   bool IsE500;
   bool IsPPC4xx;
   bool IsPPC6xx;
-  bool DeprecatedMFTB;
+  bool FeatureMFTB;
   bool DeprecatedDST;
   bool HasLazyResolverStubs;
   bool IsLittleEndian;
@@ -237,7 +237,7 @@ public:
   bool isPPC4xx() const { return IsPPC4xx; }
   bool isPPC6xx() const { return IsPPC6xx; }
   bool isE500() const { return IsE500; }
-  bool isDeprecatedMFTB() const { return DeprecatedMFTB; }
+  bool isFeatureMFTB() const { return FeatureMFTB; }
   bool isDeprecatedDST() const { return DeprecatedDST; }
   bool hasICBT() const { return HasICBT; }
   bool hasInvariantFunctionDescriptors() const {

diff --git a/test/CodeGen/PowerPC/mftb.ll b/test/CodeGen/PowerPC/mftb.ll
new file mode 100644 (file)
index 0000000..9ad9326
--- /dev/null
+++ b/test/CodeGen/PowerPC/mftb.ll
@@ -0,0 +1,72 @@
+; Check handling of the mftb instruction.
+; For CPUs 601 and pwr3, the mftb instruction should be emitted.
+; On all other CPUs (including generic, ppc, ppc64), the mfspr instruction 
+; should be used instead. There should no longer be a deprecated warning 
+; message emittedfor this instruction for any CPU.
+
+; RUN: llc -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFSPR
+; RUN: llc -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr8 < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFSPR
+; RUN: llc -mtriple=powerpc64le-unknown-linux-gnu < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFSPR
+; RUN: llc -mtriple=powerpc-unknown-linux-gnu  < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFSPR
+; RUN: llc -mtriple=powerpc-unknown-linux-gnu -mcpu=ppc < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFSPR
+; RUN: llc -mtriple=powerpc-unknown-linux-gnu -mcpu=601 < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFTB
+; RUN: llc -mtriple=powerpc-unknown-linux-gnu -mcpu=pwr3 < %s 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=CHECK-MFTB
+
+; CHECK-MFSPR-NOT: warning: deprecated
+; CHECK-MFTB-NOT: warning: deprecated
+
+define i32 @get_time() {
+       %time = call i32 asm "mftb $0, 268", "=r"()
+       ret i32 %time
+; CHECK-MFSPR-LABEL: @get_time
+; CHECK-MFSPR: mfspr 3, 268
+; CHECK-MFSPR: blr
+
+; CHECK-MFTB-LABEL: @get_time
+; CHECK-MFTB: mftb 3, 268
+; CHECK-MFTB: blr
+}
+
+define i32 @get_timeu() {
+       %time = call i32 asm "mftb $0, 269", "=r"()
+       ret i32 %time
+; CHECK-MFSPR-LABEL: @get_timeu
+; CHECK-MFSPR: mfspr 3, 269
+; CHECK-MFSPR: blr
+
+; CHECK-MFTB-LABEL: @get_timeu
+; CHECK-MFTB: mftbu 3
+; CHECK-MFTB: blr
+}
+
+define i32 @get_time_e() {
+       %time = call i32 asm "mftb $0", "=r"()
+       ret i32 %time
+; CHECK-MFSPR-LABEL: @get_time_e
+; CHECK-MFSPR: mfspr 3, 268
+; CHECK-MFSPR: blr
+
+; CHECK-MFTB-LABEL: @get_time_e
+; CHECK-MFTB: mftb 3, 268
+; CHECK-MFTB: blr
+}
+
+define i32 @get_timeu_e() {
+       %time = call i32 asm "mftbu $0", "=r"()
+       ret i32 %time
+; CHECK-MFSPR-LABEL: @get_timeu_e
+; CHECK-MFSPR: mfspr 3, 269
+; CHECK-MFSPR: blr
+
+; CHECK-MFTB-LABEL: @get_timeu_e
+; CHECK-MFTB: mftbu 3
+; CHECK-MFTB: blr
+}
+

diff --git a/test/MC/PowerPC/deprecated-p7.s b/test/MC/PowerPC/deprecated-p7.s
index 21ef6d2..6b5d912 100644 (file)
--- a/test/MC/PowerPC/deprecated-p7.s
+++ b/test/MC/PowerPC/deprecated-p7.s
@@ -3,8 +3,8 @@
 # RUN: llvm-mc -triple powerpc-unknown-linux-gnu -mcpu=601 -show-encoding < %s 2>&1 | FileCheck -check-prefix=CHECK-OLD %s
 
          mftb 3
-# CHECK: warning: deprecated
-# CHECK: mftb 3
+# CHECK-NOT: warning: deprecated
+# CHECK: mfspr 3, 268
 
 # CHECK-OLD-NOT: warning: deprecated
 # CHECK-OLD: mftb 3