[PATCH] D128122: [X86] Make sure SF is updated when optimizing for `jg/jge/jl/jle`

[Phoebe Wang via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGedcc68e86f78: [X86] Make sure SF is updated when optimizing for `jg/jge/jl/jle` (authored by pengfei).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D128122/new/

https://reviews.llvm.org/D128122

Files:
  llvm/lib/Target/X86/X86InstrInfo.cpp
  llvm/test/CodeGen/X86/pr56103.ll


Index: llvm/test/CodeGen/X86/pr56103.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/pr56103.ll
@@ -0,0 +1,65 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-linux-generic | FileCheck %s
+
+ at e = global i16 0, align 2
+ at a = global i32 0, align 4
+ at c = global i32 0, align 4
+ at b = global i64 0, align 8
+
+; Check the test instruction won't be optimizated by peephole opt.
+
+define dso_local i32 @main() nounwind {
+; CHECK-LABEL: main:
+; CHECK:       # %bb.0: # %entry
+; CHECK-NEXT:    pushq %rax
+; CHECK-NEXT:    movq e at GOTPCREL(%rip), %rax
+; CHECK-NEXT:    movw $1, (%rax)
+; CHECK-NEXT:    movq b at GOTPCREL(%rip), %rax
+; CHECK-NEXT:    movq $1, (%rax)
+; CHECK-NEXT:    movq a at GOTPCREL(%rip), %rax
+; CHECK-NEXT:    movl (%rax), %ecx
+; CHECK-NEXT:    movl $-2, %eax
+; CHECK-NEXT:    sarl %cl, %eax
+; CHECK-NEXT:    movq c at GOTPCREL(%rip), %rdx
+; CHECK-NEXT:    movl (%rdx), %edx
+; CHECK-NEXT:    decl %edx
+; CHECK-NEXT:    movzwl %ax, %eax
+; CHECK-NEXT:    decl %eax
+; CHECK-NEXT:    xorl %edx, %eax
+; CHECK-NEXT:    notl %ecx
+; CHECK-NEXT:    andl %eax, %ecx
+; CHECK-NEXT:    testq %rcx, %rcx
+; CHECK-NEXT:    jle .LBB0_2
+; CHECK-NEXT:  # %bb.1: # %if.end
+; CHECK-NEXT:    xorl %eax, %eax
+; CHECK-NEXT:    popq %rcx
+; CHECK-NEXT:    retq
+; CHECK-NEXT:  .LBB0_2: # %if.then
+; CHECK-NEXT:    callq abort at PLT
+entry:
+  store i16 1, ptr @e, align 2
+  store i64 1, ptr @b, align 8
+  %0 = load i32, ptr @a, align 4
+  %shr = ashr i32 -2, %0
+  %1 = load i32, ptr @c, align 4
+  %sub = add i32 %1, -1
+  %conv2 = zext i32 %sub to i64
+  %2 = and i32 %shr, 65535
+  %conv3 = zext i32 %2 to i64
+  %sub4 = add nsw i64 %conv3, -1
+  %xor = xor i64 %sub4, %conv2
+  %neg5 = xor i32 %0, -1
+  %conv6 = sext i32 %neg5 to i64
+  %and = and i64 %xor, %conv6
+  %cmp = icmp slt i64 %and, 1
+  br i1 %cmp, label %if.then, label %if.end
+
+if.then:                                          ; preds = %entry
+  call void @abort() #2
+  unreachable
+
+if.end:                                           ; preds = %entry
+  ret i32 0
+}
+
+declare void @abort()
Index: llvm/lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- llvm/lib/Target/X86/X86InstrInfo.cpp
+++ llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -4462,6 +4462,11 @@
         return false;
       case X86::COND_G: case X86::COND_GE:
       case X86::COND_L: case X86::COND_LE:
+        // If SF is used, but the instruction doesn't update the SF, then we
+        // can't do the optimization.
+        if (NoSignFlag)
+          return false;
+        LLVM_FALLTHROUGH;
       case X86::COND_O: case X86::COND_NO:
         // If OF is used, the instruction needs to clear it like CmpZero does.
         if (!ClearsOverflowFlag)


-------------- next part --------------
A non-text attachment was scrubbed...
Name: D128122.438518.patch
Type: text/x-patch
Size: 2878 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/llvm-commits/attachments/20220621/18948ed7/attachment.bin>