[llvm-commits] [llvm] r111709 - in /llvm/trunk: lib/Target/X86/X86FastISel.cpp test/CodeGen/X86/fast-isel-cmp-branch.ll

[Dan Gohman]

Author: djg
Date: Fri Aug 20 21:32:36 2010
New Revision: 111709

URL: http://llvm.org/viewvc/llvm-project?rev=111709&view=rev
Log:
Fix x86 fast-isel's cmp+branch folding to avoid folding when the
comparison is in a different basic block from the branch. In such
cases, the comparison's operands may not have initialized virtual
registers available.

Added:
    llvm/trunk/test/CodeGen/X86/fast-isel-cmp-branch.ll
Modified:
    llvm/trunk/lib/Target/X86/X86FastISel.cpp

Modified: llvm/trunk/lib/Target/X86/X86FastISel.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FastISel.cpp?rev=111709&r1=111708&r2=111709&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86FastISel.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86FastISel.cpp Fri Aug 20 21:32:36 2010
@@ -960,9 +960,11 @@
   MachineBasicBlock *TrueMBB = FuncInfo.MBBMap[BI->getSuccessor(0)];
   MachineBasicBlock *FalseMBB = FuncInfo.MBBMap[BI->getSuccessor(1)];
 
-  // Fold the common case of a conditional branch with a comparison.
+  // Fold the common case of a conditional branch with a comparison
+  // in the same block (values defined on other blocks may not have
+  // initialized registers).
   if (const CmpInst *CI = dyn_cast<CmpInst>(BI->getCondition())) {
-    if (CI->hasOneUse()) {
+    if (CI->hasOneUse() && CI->getParent() == I->getParent()) {
       EVT VT = TLI.getValueType(CI->getOperand(0)->getType());
 
       // Try to take advantage of fallthrough opportunities.

Added: llvm/trunk/test/CodeGen/X86/fast-isel-cmp-branch.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/fast-isel-cmp-branch.ll?rev=111709&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/X86/fast-isel-cmp-branch.ll (added)
+++ llvm/trunk/test/CodeGen/X86/fast-isel-cmp-branch.ll Fri Aug 20 21:32:36 2010
@@ -0,0 +1,29 @@
+; RUN: llc -O0 -march=x86-64 -asm-verbose=false < %s | FileCheck %s
+; rdar://8337108
+
+; Fast-isel shouldn't try to look through the compare because it's in a
+; different basic block, so its operands aren't necessarily exported
+; for cross-block usage.
+
+; CHECK: movb    %al, 7(%rsp)
+; CHECK: callq   {{_?}}bar
+; CHECK: movb    7(%rsp), %al
+
+declare void @bar()
+
+define void @foo(i32 %a, i32 %b) nounwind {
+entry:
+  %q = add i32 %a, 7
+  %r = add i32 %b, 9
+  %t = icmp ult i32 %q, %r
+  invoke void @bar() to label %next unwind label %unw
+next:
+  br i1 %t, label %true, label %return
+true:
+  call void @bar()
+  br label %return
+return:
+  ret void
+unw:
+  unreachable
+}