[ARM] Skip inline asm memory operands in DAGToDAGISel

Retry r275776 (no changes, we suspect the issue was with another commit).

The current logic for handling inline asm operands in DAGToDAGISel interprets
the operands by looking for constants, which should represent the flags
describing the kind of operand we're dealing with (immediate, memory, register
def etc). The operands representing actual data are skipped only if they are
non-const, with the exception of immediate operands which are skipped explicitly
when a flag describing an immediate is found.

The oversight is that memory operands may be const too (e.g. for device drivers
reading a fixed address), so we should explicitly skip the operand following a
flag describing a memory operand. If we don't, we risk interpreting that
constant as a flag, which is definitely not intended.

Fixes PR26038

Differential Revision: https://reviews.llvm.org/D22103

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@276101 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index c5e1d97..20db3d3 100644 (file)
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -4264,6 +4264,17 @@ bool ARMDAGToDAGISel::tryInlineAsm(SDNode *N){
     if (Changed && InlineAsm::isUseOperandTiedToDef(Flag, DefIdx))
       IsTiedToChangedOp = OpChanged[DefIdx];
 
+    // Memory operands to inline asm in the SelectionDAG are modeled with two
+    // operands: a constant of value InlineAsm::Kind_Mem followed by the input
+    // operand. If we get here and we have a Kind_Mem, skip the next operand (so
+    // it doesn't get misinterpreted), and continue. We do this here because
+    // it's important to update the OpChanged array correctly before moving on.
+    if (Kind == InlineAsm::Kind_Mem) {
+      SDValue op = N->getOperand(++i);
+      AsmNodeOperands.push_back(op);
+      continue;
+    }
+
     if (Kind != InlineAsm::Kind_RegUse && Kind != InlineAsm::Kind_RegDef
         && Kind != InlineAsm::Kind_RegDefEarlyClobber)
       continue;

diff --git a/test/CodeGen/ARM/inlineasm3.ll b/test/CodeGen/ARM/inlineasm3.ll
index eb7ba59..59706c4 100644 (file)
--- a/test/CodeGen/ARM/inlineasm3.ll
+++ b/test/CodeGen/ARM/inlineasm3.ll
@@ -121,3 +121,14 @@ entry:
   %0 = tail call <4 x i32> asm "vld1.s32 {${0:e}[], ${0:f}[]}, [$1]", "=w,r"(i32* %p) nounwind
   ret <4 x i32> %0
 }
+
+; Bugzilla PR26038
+
+define i32 @fn1() local_unnamed_addr nounwind {
+; CHECK-LABEL: fn1
+entry:
+; CHECK: mov [[addr:r[0-9]+]], #5
+; CHECK: ldrh {{.*}}[[addr]]
+  %0 = tail call i32 asm "ldrh  $0, $1", "=r,*Q"(i8* inttoptr (i32 5 to i8*)) nounwind
+  ret i32 %0
+}