[llvm] r263139 - [X86] Correctly select registers to pop into for x86_64

[Michael Kuperstein via llvm-commits]

Author: mkuper
Date: Thu Mar 10 12:43:21 2016
New Revision: 263139

URL: http://llvm.org/viewvc/llvm-project?rev=263139&view=rev
Log:
[X86] Correctly select registers to pop into for x86_64

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.

Differential Revision: http://reviews.llvm.org/D18029

Modified:
    llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
    llvm/trunk/test/CodeGen/X86/pop-stack-cleanup.ll

Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=263139&r1=263138&r2=263139&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Thu Mar 10 12:43:21 2016
@@ -2447,7 +2447,8 @@ bool X86FrameLowering::adjustStackWithPo
 
     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;
       }

Modified: llvm/trunk/test/CodeGen/X86/pop-stack-cleanup.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pop-stack-cleanup.ll?rev=263139&r1=263138&r2=263139&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/pop-stack-cleanup.ll (original)
+++ llvm/trunk/test/CodeGen/X86/pop-stack-cleanup.ll Thu Mar 10 12:43:21 2016
@@ -7,6 +7,7 @@ declare i64 @param2_ret64(i32 %a, i32 %b
 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 +75,13 @@ define void @test_linux64(i32 %size) min
   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_ret
+; LINUX64-NOT: popq %rax
+; LINUX64: retq
+  %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
+}