[PATCH] PR16258 - fadd with undef not folded

[Joey Gouly]

Hi baldrick,

This is a fix for PR16258. We do not currently fold fadd, fsub and fmul to undef.

http://llvm-reviews.chandlerc.com/D942

Files:
  lib/Analysis/InstructionSimplify.cpp
  test/Transforms/InstCombine/select-crash.ll
  test/Transforms/InstSimplify/undef.ll

Index: lib/Analysis/InstructionSimplify.cpp
===================================================================
--- lib/Analysis/InstructionSimplify.cpp
+++ lib/Analysis/InstructionSimplify.cpp
@@ -877,6 +877,10 @@
     std::swap(Op0, Op1);
   }
 
+  // fadd X, undef ==> undef
+  if (match(Op1, m_Undef()))
+    return Op1;
+
   // fadd X, -0 ==> X
   if (match(Op1, m_NegZero()))
     return Op0;
@@ -916,6 +920,10 @@
     }
   }
 
+  // fsub X, undef ==> undef
+  if (match(Op1, m_Undef()))
+    return Op1;
+
   // fsub X, 0 ==> X
   if (match(Op1, m_Zero()))
     return Op0;
@@ -956,6 +964,9 @@
     // Canonicalize the constant to the RHS.
     std::swap(Op0, Op1);
  }
+  // fmul X, undef ==> undef
+  if (match(Op1, m_Undef()))
+    return Op1;
 
  // fmul X, 1.0 ==> X
  if (match(Op1, m_FPOne()))
Index: test/Transforms/InstCombine/select-crash.ll
===================================================================
--- test/Transforms/InstCombine/select-crash.ll
+++ test/Transforms/InstCombine/select-crash.ll
@@ -4,7 +4,7 @@
 define fastcc double @gimp_operation_color_balance_map(float %value, double %highlights) nounwind readnone inlinehint {
 entry:
 ; CHECK: gimp_operation_color_balance_map
-; CHECK: fsub double -0.000000
+; CHECK: ret double undef
   %conv = fpext float %value to double
   %div = fdiv double %conv, 1.600000e+01
   %add = fadd double %div, 1.000000e+00
Index: test/Transforms/InstSimplify/undef.ll
===================================================================
--- test/Transforms/InstSimplify/undef.ll
+++ test/Transforms/InstSimplify/undef.ll
@@ -153,3 +153,24 @@
   %r = call i64 (i64)* undef(i64 %a)
   ret i64 %r
 }
+
+; CHECK: @test19
+; CHECK: ret double undef
+define double @test19(double %x) {
+  %tmp = fadd double %x, undef
+  ret double %tmp
+}
+
+; CHECK: @test20
+; CHECK: ret double undef
+define double @test20(double %x) {
+  %tmp = fsub double %x, undef
+  ret double %tmp
+}
+
+; CHECK: @test21
+; CHECK: ret double undef
+define double @test21(double %x) {
+  %tmp = fmul double %x, undef
+  ret double %tmp
+}
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