[PATCH] D18029: [X86] Correctly select registers to pop into for x86_64

[Michael Kuperstein via llvm-commits]

mkuper created this revision.
mkuper added reviewers: rnk, hans.
mkuper added a subscriber: llvm-commits.

When trying to replace an add to esp with pops, we need to choose dead registers to pop into.
Registers clobbered by the call and not imp-def'd by it should be safe. Except that it's not enough to check the register itself isn't defined, we also need to make sure no overlapping registers are defined either.

This fixes PR26711.

http://reviews.llvm.org/D18029

Files:
  lib/Target/X86/X86FrameLowering.cpp
  test/CodeGen/X86/pop-stack-cleanup.ll

Index: test/CodeGen/X86/pop-stack-cleanup.ll
===================================================================
--- test/CodeGen/X86/pop-stack-cleanup.ll
+++ test/CodeGen/X86/pop-stack-cleanup.ll
@@ -7,6 +7,7 @@
 declare void @param2(i32 %a, i32 %b)
 declare void @param3(i32 %a, i32 %b, i32 %c)
 declare void @param8(i64, i64, i64, i64, i64, i64, i64, i64)
+declare i32 @param8_ret(i64, i64, i64, i64, i64, i64, i64, i64)
 
 
 define void @test() minsize nounwind {
@@ -74,3 +75,12 @@
   call void @param8(i64 1, i64 2, i64 3, i64 4, i64 5, i64 6, i64 7, i64 8)
   ret void
 }
+
+define i32 @test_linux64_i32(i32 %size) minsize nounwind {
+; LINUX64-LABEL: test_linux64_i32:
+; LINUX64: callq param8
+; LINUX64-NOT: popq %rax
+  %a = alloca i64, i32 %size, align 8
+  %r = call i32 @param8_ret(i64 1, i64 2, i64 3, i64 4, i64 5, i64 6, i64 7, i64 8)
+  ret i32 %r
+}
Index: lib/Target/X86/X86FrameLowering.cpp
===================================================================
--- lib/Target/X86/X86FrameLowering.cpp
+++ lib/Target/X86/X86FrameLowering.cpp
@@ -2447,7 +2447,8 @@
 
     bool IsDef = false;
     for (const MachineOperand &MO : Prev->implicit_operands()) {
-      if (MO.isReg() && MO.isDef() && MO.getReg() == Candidate) {
+      if (MO.isReg() && MO.isDef() && 
+          TRI->isSuperOrSubRegisterEq(MO.getReg(), Candidate)) {
         IsDef = true;
         break;
       }


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