Always adjust the stack pointer immediately after the call.

Some x86-32 calls pop values off the stack, and we need to readjust the
stack pointer after the call. This happens when ADJCALLSTACKUP is
eliminated.

It could happen that spill code was inserted between the CALL and
ADJCALLSTACKUP instructions, and we would compute wrong stack pointer
offsets for those frame index references.

Fix this by inserting the stack pointer adjustment immediately after the
call instead of where the ADJCALLSTACKUP instruction was erased.

I don't have a test case since we don't currently insert code in that
position. We will soon, though. I am testing a regalloc patch that
didn't work on Linux because of this.

llvm-svn: 134113

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86RegisterInfo.cpp b/llvm/lib/Target/X86/X86RegisterInfo.cpp
index 90b333f4b50..c0ce81a5cb0 100644
--- a/llvm/lib/Target/X86/X86RegisterInfo.cpp
+++ b/llvm/lib/Target/X86/X86RegisterInfo.cpp
@@ -662,6 +662,13 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
 
     // The EFLAGS implicit def is dead.
     New->getOperand(3).setIsDead();
+
+    // We are not tracking the stack pointer adjustment by the callee, so make
+    // sure we restore the stack pointer immediately after the call, there may
+    // be spill code inserted between the CALL and ADJCALLSTACKUP instructions.
+    MachineBasicBlock::iterator B = MBB.begin();
+    while (I != B && !llvm::prior(I)->getDesc().isCall())
+      --I;
     MBB.insert(I, New);
   }
 }