[PATCH] D93983: RegAllocFast: Do not free later early-clobbered registers.

[Freddy, Ye via Phabricator via llvm-commits]

FreddyYe created this revision.
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Consider corner case: MSInlineAsm may contain operands of both
`implicit-def $eax` and `implicit-def early-clobber $eax`


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D93983

Files:
  llvm/lib/CodeGen/RegAllocFast.cpp
  llvm/test/CodeGen/X86/phys-msInline-fastregalloc.ll


Index: llvm/test/CodeGen/X86/phys-msInline-fastregalloc.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/phys-msInline-fastregalloc.ll
@@ -0,0 +1,15 @@
+; RUN: llc < %s -O0 -mtriple=i386-unknown-linux-gnu -mcpu=generic -regalloc=fast -optimize-regalloc=0 -no-x86-call-frame-opt | FileCheck %s
+
+define dso_local i32 @main() {
+entry:
+; CHECK: movl $1, %eax
+; CHECK-NOT: movl %eax, (%eax)
+  %retval = alloca i32, align 4
+  %c = alloca { [4 x i32] }, align 4
+  store i32 0, i32* %retval, align 4
+  %m32 = bitcast { [4 x i32] }* %c to [4 x i32]*
+  %0 = call i32 asm sideeffect inteldialect "mov eax,$$1\0A\09mov $0,eax", "=*m,={eax},~{eax},~{dirflag},~{fpsr},~{flags}"([4 x i32]* %m32) #1, !srcloc !3
+  store i32 %0, i32* %retval, align 4
+  ret i32 0
+}
+!3 = !{i32 285}
\ No newline at end of file
Index: llvm/lib/CodeGen/RegAllocFast.cpp
===================================================================
--- llvm/lib/CodeGen/RegAllocFast.cpp
+++ llvm/lib/CodeGen/RegAllocFast.cpp
@@ -1237,6 +1237,18 @@
       Register Reg = MO.getReg();
       if (!Reg)
         continue;
+      // Do not free later early-clobbered registers when MI is MSVCInlineAsm
+      if (MI.isMSInlineAsm()) {
+        unsigned J = 0;
+        for (J = I+1; J != MI.getNumOperands(); ++J) {
+          MachineOperand &LaterMO = MI.getOperand(J);
+          if (LaterMO.isReg() && LaterMO.getReg() == Reg &&
+              MI.getOperand(J).isEarlyClobber())
+            break;
+        }
+        if (J != MI.getNumOperands())
+          continue;
+      }
       assert(Reg.isPhysical());
       if (MRI->isReserved(Reg))
         continue;


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