[FastISel] Let the target decide first if it wants to materialize a constant.

This changes the order in which FastISel tries to materialize a constant.
Originally it would try to use a simple target-independent approach, which
can lead to the generation of inefficient code.

On X86 this would result in the use of movabsq to materialize any 64bit
integer constant - even for simple and small values such as 0 and 1. Also
some very funny floating-point materialization could be observed too.

On AArch64 it would materialize the constant 0 in a register even the
architecture has an actual "zero" register.

On ARM it would generate unnecessary mov instructions or not use mvn.

This change simply changes the order and always asks the target first if it
likes to materialize the constant. This doesn't fix all the issues
mentioned above, but it enables the targets to implement such
optimizations.

Related to <rdar://problem/17420988>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@215588 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/FastISel.h b/include/llvm/CodeGen/FastISel.h
index 7af25db..b0503f0 100644 (file)
--- a/include/llvm/CodeGen/FastISel.h
+++ b/include/llvm/CodeGen/FastISel.h
@@ -575,6 +575,10 @@ private:
   /// correspond to a different MBB than the end.
   bool HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB);
 
+  /// \brief Helper for materializeRegForValue to materialize a constant in a
+  /// target-independent way.
+  unsigned MaterializeConstant(const Value *V, MVT VT);
+
   /// Helper for getRegForVale. This function is called when the value isn't
   /// already available in a register and must be materialized with new
   /// instructions.

diff --git a/lib/CodeGen/SelectionDAG/FastISel.cpp b/lib/CodeGen/SelectionDAG/FastISel.cpp
index 1c2cee2..93a366a 100644 (file)
--- a/lib/CodeGen/SelectionDAG/FastISel.cpp
+++ b/lib/CodeGen/SelectionDAG/FastISel.cpp
@@ -198,29 +198,24 @@ unsigned FastISel::getRegForValue(const Value *V) {
   return Reg;
 }
 
-/// materializeRegForValue - Helper for getRegForValue. This function is
-/// called when the value isn't already available in a register and must
-/// be materialized with new instructions.
-unsigned FastISel::materializeRegForValue(const Value *V, MVT VT) {
+unsigned FastISel::MaterializeConstant(const Value *V, MVT VT) {
   unsigned Reg = 0;
-
   if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
     if (CI->getValue().getActiveBits() <= 64)
       Reg = FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
-  } else if (isa<AllocaInst>(V)) {
+  } else if (isa<AllocaInst>(V))
     Reg = TargetMaterializeAlloca(cast<AllocaInst>(V));
-  } else if (isa<ConstantPointerNull>(V)) {
+  else if (isa<ConstantPointerNull>(V))
     // Translate this as an integer zero so that it can be
     // local-CSE'd with actual integer zeros.
     Reg =
       getRegForValue(Constant::getNullValue(DL.getIntPtrType(V->getContext())));
-  } else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
-    if (CF->isNullValue()) {
+  else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
+    if (CF->isNullValue())
       Reg = TargetMaterializeFloatZero(CF);
-    } else {
+    else
       // Try to emit the constant directly.
       Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
-    }
 
     if (!Reg) {
       // Try to emit the constant by using an integer constant with a cast.
@@ -253,15 +248,26 @@ unsigned FastISel::materializeRegForValue(const Value *V, MVT VT) {
     BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DbgLoc,
             TII.get(TargetOpcode::IMPLICIT_DEF), Reg);
   }
+  return Reg;
+}
 
-  // If target-independent code couldn't handle the value, give target-specific
-  // code a try.
-  if (!Reg && isa<Constant>(V))
+/// materializeRegForValue - Helper for getRegForValue. This function is
+/// called when the value isn't already available in a register and must
+/// be materialized with new instructions.
+unsigned FastISel::materializeRegForValue(const Value *V, MVT VT) {
+  unsigned Reg = 0;
+  // Give the target-specific code a try first.
+  if (isa<Constant>(V))
     Reg = TargetMaterializeConstant(cast<Constant>(V));
 
+  // If target-specific code couldn't or didn't want to handle the value, then
+  // give target-independent code a try.
+  if (!Reg)
+    Reg = MaterializeConstant(V, VT);
+
   // Don't cache constant materializations in the general ValueMap.
   // To do so would require tracking what uses they dominate.
-  if (Reg != 0) {
+  if (Reg) {
     LocalValueMap[V] = Reg;
     LastLocalValue = MRI.getVRegDef(Reg);
   }

diff --git a/test/CodeGen/ARM/fast-isel-call.ll b/test/CodeGen/ARM/fast-isel-call.ll
index 9d9e341..74b31bd 100644 (file)
--- a/test/CodeGen/ARM/fast-isel-call.ll
+++ b/test/CodeGen/ARM/fast-isel-call.ll
@@ -117,17 +117,11 @@ entry:
 ; ARM-LONG: blx [[R]]
 ; THUMB: @t10
 ; THUMB: movs [[R0:l?r[0-9]*]], #0
-; THUMB: movt [[R0]], #0
 ; THUMB: movs [[R1:l?r[0-9]*]], #248
-; THUMB: movt [[R1]], #0
 ; THUMB: movs [[R2:l?r[0-9]*]], #187
-; THUMB: movt [[R2]], #0
 ; THUMB: movs [[R3:l?r[0-9]*]], #28
-; THUMB: movt [[R3]], #0
 ; THUMB: movw [[R4:l?r[0-9]*]], #40
-; THUMB: movt [[R4]], #0
 ; THUMB: movw [[R5:l?r[0-9]*]], #186
-; THUMB: movt [[R5]], #0
 ; THUMB: and [[R0]], [[R0]], #255
 ; THUMB: and [[R1]], [[R1]], #255
 ; THUMB: and [[R2]], [[R2]], #255

diff --git a/test/CodeGen/ARM/fast-isel-deadcode.ll b/test/CodeGen/ARM/fast-isel-deadcode.ll
index 5e6666c..c3eed30 100644 (file)
--- a/test/CodeGen/ARM/fast-isel-deadcode.ll
+++ b/test/CodeGen/ARM/fast-isel-deadcode.ll
@@ -14,7 +14,6 @@ entry:
 ; THUMB-NOT: ldr
 ; THUMB-NOT: sxtb
 ; THUMB: movs r0, #0
-; THUMB: movt r0, #0
 ; THUMB: pop
   ret i32 0
 }

diff --git a/test/CodeGen/ARM/fast-isel-intrinsic.ll b/test/CodeGen/ARM/fast-isel-intrinsic.ll
index 089209e..b09931d 100644 (file)
--- a/test/CodeGen/ARM/fast-isel-intrinsic.ll
+++ b/test/CodeGen/ARM/fast-isel-intrinsic.ll
@@ -31,9 +31,7 @@ define void @t1() nounwind ssp {
 ; THUMB: {{(movt r0, :upper16:_?message1)|(ldr r0, \[r0\])}}
 ; THUMB: adds r0, #5
 ; THUMB: movs r1, #64
-; THUMB: movt r1, #0
 ; THUMB: movs r2, #10
-; THUMB: movt r2, #0
 ; THUMB: and r1, r1, #255
 ; THUMB: bl {{_?}}memset
 ; THUMB-LONG-LABEL: t1:
@@ -71,7 +69,6 @@ define void @t2() nounwind ssp {
 ; THUMB: adds r1, r0, #4
 ; THUMB: adds r0, #16
 ; THUMB: movs r2, #17
-; THUMB: movt r2, #0
 ; THUMB: str r0, [sp[[SLOT:[, #0-9]*]]] @ 4-byte Spill
 ; THUMB: mov r0, r1
 ; THUMB: ldr r1,  [sp[[SLOT]]] @ 4-byte Reload
@@ -109,7 +106,6 @@ define void @t3() nounwind ssp {
 ; THUMB: adds r1, r0, #4
 ; THUMB: adds r0, #16
 ; THUMB: movs r2, #10
-; THUMB: movt r2, #0
 ; THUMB: str r0, [sp[[SLOT:[, #0-9]*]]] @ 4-byte Spill
 ; THUMB: mov r0, r1
 ; THUMB: ldr r1,  [sp[[SLOT]]] @ 4-byte Reload

diff --git a/test/CodeGen/ARM/fast-isel-mvn.ll b/test/CodeGen/ARM/fast-isel-mvn.ll
index 9cb56ea..7ec7f3c 100644 (file)
--- a/test/CodeGen/ARM/fast-isel-mvn.ll
+++ b/test/CodeGen/ARM/fast-isel-mvn.ll
@@ -1,17 +1,13 @@
 ; RUN: llc -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -arm-use-movt=false -mtriple=armv7-apple-ios     < %s | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
 ; RUN: llc -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -arm-use-movt=false -mtriple=armv7-linux-gnueabi < %s | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
-; RUN: llc < %s -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -mtriple=thumbv7-apple-ios | FileCheck %s --check-prefix=THUMB
+; RUN: llc -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -arm-use-movt=false -mtriple=thumbv7-apple-ios   < %s | FileCheck %s --check-prefix=CHECK --check-prefix=ARM
+; RUN: llc -O0 -verify-machineinstrs -fast-isel-abort -relocation-model=dynamic-no-pic -arm-use-movt=true  -mtriple=thumbv7-apple-ios   < %s | FileCheck %s --check-prefix=CHECK --check-prefix=THUMB
 ; rdar://10412592
 
-; Note: The Thumb code is being generated by the target-independent selector.
-
 define void @t1() nounwind {
 entry:
-; ARM: t1
-; THUMB: t1
-; ARM: mvn r0, #0
-; THUMB: movw r0, #65535
-; THUMB: movt r0, #65535
+; CHECK-LABEL: t1
+; CHECK:       mvn r0, #0
   call void @foo(i32 -1)
   ret void
 }
@@ -20,22 +16,16 @@ declare void @foo(i32)
 
 define void @t2() nounwind {
 entry:
-; ARM: t2
-; THUMB: t2
-; ARM: mvn r0, #233
-; THUMB: movw r0, #65302
-; THUMB: movt r0, #65535
+; CHECK-LABEL: t2
+; CHECK:       mvn r0, #233
   call void @foo(i32 -234)
   ret void
 }
 
 define void @t3() nounwind {
 entry:
-; ARM: t3
-; THUMB: t3
-; ARM: mvn     r0, #256
-; THUMB: movw r0, #65279
-; THUMB: movt r0, #65535
+; CHECK-LABEL: t3
+; CHECK:       mvn r0, #256
   call void @foo(i32 -257)
   ret void
 }
@@ -43,66 +33,51 @@ entry:
 ; Load from constant pool
 define void @t4() nounwind {
 entry:
-; ARM: t4
-; THUMB: t4
-; ARM: ldr     r0
-; THUMB: movw r0, #65278
-; THUMB: movt r0, #65535
+; ARM-LABEL:   t4
+; ARM:         ldr r0
+; THUMB-LABEL: t4
+; THUMB:       movw r0, #65278
+; THUMB:       movt r0, #65535
   call void @foo(i32 -258)
   ret void
 }
 
 define void @t5() nounwind {
 entry:
-; ARM: t5
-; THUMB: t5
-; ARM: mvn r0, #65280
-; THUMB: movs r0, #255
-; THUMB: movt r0, #65535
+; CHECK-LABEL: t5
+; CHECK:       mvn r0, #65280
   call void @foo(i32 -65281)
   ret void
 }
 
 define void @t6() nounwind {
 entry:
-; ARM: t6
-; THUMB: t6
-; ARM: mvn r0, #978944
-; THUMB: movw r0, #4095
-; THUMB: movt r0, #65521
+; CHECK-LABEL: t6
+; CHECK:       mvn r0, #978944
   call void @foo(i32 -978945)
   ret void
 }
 
 define void @t7() nounwind {
 entry:
-; ARM: t7
-; THUMB: t7
-; ARM: mvn r0, #267386880
-; THUMB: movw r0, #65535
-; THUMB: movt r0, #61455
+; CHECK-LABEL: t7
+; CHECK:       mvn r0, #267386880
   call void @foo(i32 -267386881)
   ret void
 }
 
 define void @t8() nounwind {
 entry:
-; ARM: t8
-; THUMB: t8
-; ARM: mvn r0, #65280
-; THUMB: movs r0, #255
-; THUMB: movt r0, #65535
+; CHECK-LABEL: t8
+; CHECK:       mvn r0, #65280
   call void @foo(i32 -65281)
   ret void
 }
 
 define void @t9() nounwind {
 entry:
-; ARM: t9
-; THUMB: t9
-; ARM: mvn r0, #2130706432
-; THUMB: movw r0, #65535
-; THUMB: movt r0, #33023
+; CHECK-LABEL: t9
+; CHECK:       mvn r0, #2130706432
   call void @foo(i32 -2130706433)
   ret void
 }

diff --git a/test/CodeGen/ARM/fast-isel-select.ll b/test/CodeGen/ARM/fast-isel-select.ll
index 40f8807..549c97e 100644 (file)
--- a/test/CodeGen/ARM/fast-isel-select.ll
+++ b/test/CodeGen/ARM/fast-isel-select.ll
@@ -12,7 +12,6 @@ entry:
 ; ARM: mov r0, r{{[1-9]}}
 ; THUMB: t1
 ; THUMB: movs r{{[1-9]}}, #10
-; THUMB: movt r{{[1-9]}}, #0
 ; THUMB: cmp r0, #0
 ; THUMB: it eq
 ; THUMB: moveq r{{[1-9]}}, #20
@@ -59,13 +58,12 @@ entry:
 ; ARM: cmp r0, #0
 ; ARM: mvneq r{{[1-9]}}, #0
 ; ARM: mov r0, r{{[1-9]}}
-; THUMB: t4
-; THUMB: movw r{{[1-9]}}, #65526
-; THUMB: movt r{{[1-9]}}, #65535
+; THUMB-LABEL: t4
+; THUMB: mvn [[REG:r[1-9]+]], #9
 ; THUMB: cmp r0, #0
 ; THUMB: it eq
-; THUMB: mvneq r{{[1-9]}}, #0
-; THUMB: mov r0, r{{[1-9]}}
+; THUMB: mvneq [[REG]], #0
+; THUMB: mov r0, [[REG]]
   %0 = select i1 %c, i32 -10, i32 -1
   ret i32 %0
 }

diff --git a/test/CodeGen/ARM/fast-isel-vararg.ll b/test/CodeGen/ARM/fast-isel-vararg.ll
index 0b7b0bd..3ff2b15 100644 (file)
--- a/test/CodeGen/ARM/fast-isel-vararg.ll
+++ b/test/CodeGen/ARM/fast-isel-vararg.ll
@@ -29,7 +29,6 @@ entry:
 ; ARM: bl {{_?CallVariadic}}
 ; THUMB: sub sp, #32
 ; THUMB: movs r0, #5
-; THUMB: movt r0, #0
 ; THUMB: ldr r1, [sp, #28]
 ; THUMB: ldr r2, [sp, #24]
 ; THUMB: ldr r3, [sp, #20]

diff --git a/test/CodeGen/PowerPC/fast-isel-call.ll b/test/CodeGen/PowerPC/fast-isel-call.ll
index 33a8ba9..2230905 100644 (file)
--- a/test/CodeGen/PowerPC/fast-isel-call.ll
+++ b/test/CodeGen/PowerPC/fast-isel-call.ll
@@ -57,11 +57,11 @@ entry:
 ; ELF64: t10
   %call = call i32 @bar(i8 zeroext 0, i8 zeroext -8, i8 zeroext -69, i8 zeroext 28, i8 zeroext 40, i8 zeroext -70)
 ; ELF64: li 3, 0
-; ELF64: li 4, 248
-; ELF64: li 5, 187
+; ELF64: li 4, -8
+; ELF64: li 5, -69
 ; ELF64: li 6, 28
 ; ELF64: li 7, 40
-; ELF64: li 8, 186
+; ELF64: li 8, -70
 ; ELF64: rldicl 3, 3, 0, 56
 ; ELF64: rldicl 4, 4, 0, 56
 ; ELF64: rldicl 5, 5, 0, 56

diff --git a/test/CodeGen/X86/fast-isel-x86-64.ll b/test/CodeGen/X86/fast-isel-x86-64.ll
index f7d2750..29f1f26 100644 (file)
--- a/test/CodeGen/X86/fast-isel-x86-64.ll
+++ b/test/CodeGen/X86/fast-isel-x86-64.ll
@@ -194,12 +194,10 @@ define void @test16() nounwind {
   br label %block2
 
 block2:
-; CHECK: movabsq $1
-; CHECK: cvtsi2sdq {{.*}} %xmm0
+; CHECK: movsd LCP{{.*}}_{{.*}}(%rip), %xmm0
 ; CHECK: movb $1, %al
 ; CHECK: callq _test16callee
 
-; AVX: movabsq $1
 ; AVX: vmovsd LCP{{.*}}_{{.*}}(%rip), %xmm0
 ; AVX: movb $1, %al
 ; AVX: callq _test16callee