ARM SelectDYN_ALLOC should emit a copy from SP rather than referencing SP directly...

llvm is generating poor code for dynamic alloca, I'll fix that later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101383 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMISelDAGToDAG.cpp b/lib/Target/ARM/ARMISelDAGToDAG.cpp
index 7d486631897a2f77933d1c4be4b0351b887c5798..2f24d2ea1c6929399bd9d638d8e82f3d4d141d0f 100644 (file)
--- a/lib/Target/ARM/ARMISelDAGToDAG.cpp
+++ b/lib/Target/ARM/ARMISelDAGToDAG.cpp
@@ -945,7 +945,7 @@ SDNode *ARMDAGToDAGISel::SelectDYN_ALLOC(SDNode *N) {
   SDValue Chain = N->getOperand(0);
   SDValue Size = N->getOperand(1);
   SDValue Align = N->getOperand(2);
-  SDValue SP = CurDAG->getRegister(ARM::SP, MVT::i32);
+  SDValue SP = CurDAG->getCopyFromReg(Chain, dl, ARM::SP, MVT::i32);
   int32_t AlignVal = cast<ConstantSDNode>(Align)->getSExtValue();
   if (AlignVal < 0)
     // We need to align the stack. Use Thumb1 tAND which is the only thumb

diff --git a/test/CodeGen/Thumb2/2010-04-15-DynAllocBug.ll b/test/CodeGen/Thumb2/2010-04-15-DynAllocBug.ll
new file mode 100644 (file)
index 0000000..329494b
--- /dev/null
+++ b/test/CodeGen/Thumb2/2010-04-15-DynAllocBug.ll
@@ -0,0 +1,23 @@
+; RUN: llc < %s -mtriple=thumbv7-apple-darwin -mcpu=cortex-a8 -O3 | FileCheck %s
+; rdar://7493908
+
+; Make sure the result of the first dynamic_alloc isn't copied back to sp more
+; than once. We'll deal with poor codegen later.
+
+define arm_apcscc void @t() nounwind ssp {
+entry:
+; CHECK: t:
+; CHECK: mvn r0, #7
+; CHECK: ands sp, r0
+; CHECK: mov r1, sp
+; CHECK: mov sp, r1
+; Yes, this is stupid codegen, but it's correct.
+; CHECK: sub sp, #16
+; CHECK: mov r1, sp
+; CHECK: mov sp, r1
+; CHECK: ands sp, r0
+  %size = mul i32 8, 2
+  %vla_a = alloca i8, i32 %size, align 8
+  %vla_b = alloca i8, i32 %size, align 8
+  unreachable
+}