[PATCH] Fix checked arithmetic for i8 on X86

[Keno Fischer]

Added test. Simplified conditional.

http://reviews.llvm.org/D3920

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/i8-umulo.ll

Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -11469,8 +11469,9 @@
   }
 
   if (addTest) {
-    CC = DAG.getConstant(X86::COND_NE, MVT::i8);
-    Cond = EmitTest(Cond, X86::COND_NE, dl, DAG);
+    X86::CondCode X86Cond = Inverted ? X86::COND_E : X86::COND_NE;
+    CC = DAG.getConstant(X86Cond, MVT::i8);
+    Cond = EmitTest(Cond, X86Cond, dl, DAG);
   }
   Cond = ConvertCmpIfNecessary(Cond, DAG);
   return DAG.getNode(X86ISD::BRCOND, dl, Op.getValueType(),
Index: test/CodeGen/X86/i8-umulo.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/i8-umulo.ll
@@ -0,0 +1,23 @@
+; RUN: llc -mcpu=generic -march=x86 < %s | FileCheck %s
+
+declare {i8, i1} @llvm.umul.with.overflow.i8(i8 %a, i8 %b)
+define i8 @testumulo(i32 %argc) {
+; CHECK: imulw
+; CHECK: testb %{{.+}}, %{{.+}}
+; CHECK: je [[NOOVERFLOWLABEL:.+]]
+; CHECK: {{.*}}[[NOOVERFLOWLABEL]]:
+; CHECK-NEXT: movb
+; CHECK-NEXT: retl
+top:
+  %RHS = trunc i32 %argc to i8
+  %umul = call { i8, i1 } @llvm.umul.with.overflow.i8(i8 25, i8 %RHS)
+  %ex = extractvalue { i8, i1 } %umul, 1
+  br i1 %ex, label %overflow, label %nooverlow
+
+overflow:
+  ret i8 %RHS
+
+nooverlow:
+  %umul.value = extractvalue { i8, i1 } %umul, 0
+  ret i8 %umul.value
+}
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