[PATCH] D77031: [X86] make sure POP has implicit def/use of stack pointer when materializing 8-bit immediates for minsize

[Yuanfang Chen via Phabricator via llvm-commits]

ychen created this revision.
ychen added a reviewer: craig.topper.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

Otherwise PostRA list scheduler may reorder instruction, such as

schedule this
'''
pushq  $0x8
pop    %rbx
lea    0x2a0(%rsp),%r15
'''
to
'''
pushq  $0x8
lea    0x2a0(%rsp),%r15
pop    %rbx
'''
by mistake. The patch is to prevent this to happen by making sure POP has
implicit use of SP.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77031

Files:
  llvm/lib/Target/X86/X86InstrInfo.cpp
  llvm/test/CodeGen/X86/materialize.ll


Index: llvm/test/CodeGen/X86/materialize.ll
===================================================================
--- llvm/test/CodeGen/X86/materialize.ll
+++ llvm/test/CodeGen/X86/materialize.ll
@@ -2,6 +2,13 @@
 ; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mattr=+cmov %s -o - | FileCheck %s --check-prefix=CHECK64
 ; RUN: llc -mtriple=x86_64-pc-win32 -mattr=+cmov %s -o - | FileCheck %s --check-prefix=CHECKWIN64
 
+; RUN: llc -mtriple=i686-unknown-linux-gnu -mattr=+cmov %s -o /dev/null \
+; RUN:     -print-after postrapseudos -filter-print-funcs pr26023 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=OPERAND32
+; RUN: llc -mtriple=x86_64-unknown-linux-gnu -mattr=+cmov %s -o /dev/null \
+; RUN:     -print-after postrapseudos -filter-print-funcs one64_minsize 2>&1 \
+; RUN:    | FileCheck %s --check-prefix=OPERAND64
+
 define i32 @one32_nooptsize() {
 entry:
   ret i32 1
@@ -92,6 +99,12 @@
 ; CHECK32:       pushl $5
 ; CHECK32:       popl %ecx
 ; CHECK32:       retl
+
+; Check push/pop have implicit def/use of $esp
+; OPERAND32:      PUSH32i8 5, implicit-def $esp, implicit $esp
+; OPERAND32-NEXT: CFI_INSTRUCTION adjust_cfa_offset 4
+; OPERAND32-NEXT: renamable $ecx = POP32r implicit-def $esp, implicit $esp
+; OPERAND32-NEXT: CFI_INSTRUCTION adjust_cfa_offset -4
 }
 
 
@@ -110,6 +123,13 @@
 ; CHECKWIN64-LABEL: one64_minsize:
 ; CHECKWIN64:       movl $1, %eax
 ; CHECKWIN64-NEXT:  retq
+
+; Check push/pop have implicit def/use of $rsp
+; OPERAND64:      PUSH64i8 1, implicit-def $rsp, implicit $rsp
+; OPERAND64-NEXT: CFI_INSTRUCTION adjust_cfa_offset 8
+; OPERAND64-NEXT: $rax = POP64r implicit-def $rsp, implicit $rsp
+; OPERAND64-NEXT: CFI_INSTRUCTION adjust_cfa_offset -8
+; OPERAND64-NEXT: RET 0, $rax
 }
 
 define i32 @minus_one32() optsize {
Index: llvm/lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- llvm/lib/Target/X86/X86InstrInfo.cpp
+++ llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -4443,6 +4443,8 @@
     BuildMI(MBB, I, DL, TII.get(X86::PUSH32i8)).addImm(Imm);
     MIB->setDesc(TII.get(X86::POP32r));
   }
+  MIB->RemoveOperand(1);
+  MIB->addImplicitDefUseOperands(*MBB.getParent());
 
   // Build CFI if necessary.
   MachineFunction &MF = *MBB.getParent();


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