Index: lib/IR/Instruction.cpp
===================================================================
--- lib/IR/Instruction.cpp
+++ lib/IR/Instruction.cpp
@@ -602,7 +602,8 @@
   switch (Opcode) {
   case FMul:
   case FAdd:
-    return cast<FPMathOperator>(this)->isFast();
+    return cast<FPMathOperator>(this)->hasAllowReassoc() &&
+           cast<FPMathOperator>(this)->hasNoSignedZeros();
   default:
     return false;
   }
Index: test/Transforms/InstCombine/2006-10-26-VectorReassoc.ll
===================================================================
--- test/Transforms/InstCombine/2006-10-26-VectorReassoc.ll
+++ test/Transforms/InstCombine/2006-10-26-VectorReassoc.ll
@@ -1,10 +1,145 @@
 ; RUN: opt < %s -instcombine -S | FileCheck %s
-; CHECK: mul
-; CHECK: mul
 
-define <4 x float> @test(<4 x float> %V) {
-        %Y = fmul <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >                ; <<4 x float>> [#uses=1]
-        %Z = fmul <4 x float> %Y, < float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00 >               ; <<4 x float>> [#uses=1]
+; (V * C1) * C2 => V * (C1 * C2)
+; Verify this doesn't fold when no fast-math-flags are specified
+define <4 x float> @test_fmul(<4 x float> %V) {
+; CHECK-LABEL: @test_fmul(
+; CHECK-NEXT:     [[TMP1:%.*]] = fmul <4 x float> [[V:%.*]], <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     [[TMP2:%.*]] = fmul <4 x float> [[TMP1]], <float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     ret <4 x float> [[TMP2]]
+        %Y = fmul <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fmul <4 x float> %Y, < float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00 >
         ret <4 x float> %Z
 }
 
+; (V * C1) * C2 => V * (C1 * C2)
+; Verify this folds with 'fast'
+define <4 x float> @test_fmul_fast(<4 x float> %V) {
+; CHECK-LABEL: @test_fmul_fast(
+; CHECK-NEXT:     [[TMP1:%.*]] = fmul fast <4 x float> [[V:%.*]], <float 1.000000e+00, float 4.000000e+05, float -9.000000e+00, float 1.600000e+01>
+; CHECK-NEXT:     ret <4 x float> [[TMP1]]
+        %Y = fmul fast <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fmul fast <4 x float> %Y, < float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; (V * C1) * C2 => V * (C1 * C2)
+; Verify this folds with 'reassoc' and 'nsz' ('nsz' not technically required)
+define <4 x float> @test_fmul_reassoc_nsz(<4 x float> %V) {
+; CHECK-LABEL: @test_fmul_reassoc_nsz(
+; CHECK-NEXT:     [[TMP1:%.*]] = fmul reassoc nsz <4 x float> [[V:%.*]], <float 1.000000e+00, float 4.000000e+05, float -9.000000e+00, float 1.600000e+01>
+; CHECK-NEXT:     ret <4 x float> [[TMP1]]
+        %Y = fmul reassoc nsz <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fmul reassoc nsz <4 x float> %Y, < float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; (V * C1) * C2 => V * (C1 * C2)
+; TODO: This doesn't require 'nsz'.  It should fold to V * { 1.0, 4.0e+05, -9.0, 16.0 }
+define <4 x float> @test_fmul_reassoc(<4 x float> %V) {
+; CHECK-LABEL: @test_fmul_reassoc(
+; CHECK-NEXT:     [[TMP1:%.*]] = fmul reassoc <4 x float> [[V:%.*]], <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     [[TMP2:%.*]] = fmul reassoc <4 x float> [[TMP1]], <float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     ret <4 x float> [[TMP2]]
+        %Y = fmul reassoc <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fmul reassoc <4 x float> %Y, < float 1.000000e+00, float 2.000000e+05, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; (V + C1) + C2 => V + (C1 + C2)
+; Verify this doesn't fold when no fast-math-flags are specified
+define <4 x float> @test_fadd(<4 x float> %V) {
+; CHECK-LABEL: @test_fadd(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd <4 x float> [[V:%.*]], <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     [[TMP2:%.*]] = fadd <4 x float> [[TMP1]], <float 1.000000e+00, float 2.000000e+00, float -3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     ret <4 x float> [[TMP2]]
+        %Y = fadd <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fadd <4 x float> %Y, < float 1.000000e+00, float 2.000000e+00, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; (V + C1) + C2 => V + (C1 + C2)
+; Verify this folds with 'fast'
+define <4 x float> @test_fadd_fast(<4 x float> %V) {
+; CHECK-LABEL: @test_fadd_fast(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd fast <4 x float> [[V:%.*]], <float 2.000000e+00, float 4.000000e+00, float 0.000000e+00, float 8.000000e+00>
+; CHECK-NEXT:     ret <4 x float> [[TMP1]]
+        %Y = fadd fast <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fadd fast <4 x float> %Y, < float 1.000000e+00, float 2.000000e+00, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; (V + C1) + C2 => V + (C1 + C2)
+; Verify this folds with 'reassoc' and 'nsz' ('nsz' not technically required)
+define <4 x float> @test_fadd_reassoc_nsz(<4 x float> %V) {
+; CHECK-LABEL: @test_fadd_reassoc_nsz(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd reassoc nsz <4 x float> [[V:%.*]], <float 2.000000e+00, float 4.000000e+00, float 0.000000e+00, float 8.000000e+00>
+; CHECK-NEXT:     ret <4 x float> [[TMP1]]
+        %Y = fadd reassoc nsz <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fadd reassoc nsz <4 x float> %Y, < float 1.000000e+00, float 2.000000e+00, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; (V + C1) + C2 => V + (C1 + C2)
+; TODO: This doesn't require 'nsz'.  It should fold to V + { 2.0, 4.0, 0.0, 8.0 }
+define <4 x float> @test_fadd_reassoc(<4 x float> %V) {
+; CHECK-LABEL: @test_fadd_reassoc(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd reassoc <4 x float> [[V:%.*]], <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     [[TMP2:%.*]] = fadd reassoc <4 x float> [[TMP1]], <float 1.000000e+00, float 2.000000e+00, float -3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     ret <4 x float> [[TMP2]]
+        %Y = fadd reassoc <4 x float> %V, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Z = fadd reassoc <4 x float> %Y, < float 1.000000e+00, float 2.000000e+00, float -3.000000e+00, float 4.000000e+00 >
+        ret <4 x float> %Z
+}
+
+; ( A + C1 ) + ( B + -C1 )
+; Verify this doesn't fold when no fast-math-flags are specified
+define <4 x float> @test_fadds_cancel_(<4 x float> %A, <4 x float> %B) {
+; CHECK-LABEL: @test_fadds_cancel_(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd <4 x float> [[A:%.*]], <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     [[TMP2:%.*]] = fadd <4 x float> [[B:%.*]], <float -1.000000e+00, float -2.000000e+00, float -3.000000e+00, float -4.000000e+00>
+; CHECK-NEXT:     [[TMP3:%.*]] = fadd <4 x float> [[TMP1]], [[TMP2]]
+; CHECK-NEXT:     ret <4 x float> [[TMP3]]
+        %X = fadd <4 x float> %A, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Y = fadd <4 x float> %B, < float -1.000000e+00, float -2.000000e+00, float -3.000000e+00, float -4.000000e+00 >
+        %Z = fadd <4 x float> %X, %Y
+        ret <4 x float> %Z
+}
+
+; ( A + C1 ) + ( B + -C1 )
+; Verify this folds to 'A + B' with 'fast'
+define <4 x float> @test_fadds_cancel_fast(<4 x float> %A, <4 x float> %B) {
+; CHECK-LABEL: @test_fadds_cancel_fast(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd fast <4 x float> [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:     ret <4 x float> [[TMP1]]
+        %X = fadd fast <4 x float> %A, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Y = fadd fast <4 x float> %B, < float -1.000000e+00, float -2.000000e+00, float -3.000000e+00, float -4.000000e+00 >
+        %Z = fadd fast <4 x float> %X, %Y
+        ret <4 x float> %Z
+}
+
+; ( A + C1 ) + ( B + -C1 )
+; Verify this folds to 'A + B' with 'reassoc' and 'nsz' ('nsz' is required)
+define <4 x float> @test_fadds_cancel_reassoc_nsz(<4 x float> %A, <4 x float> %B) {
+; CHECK-LABEL: @test_fadds_cancel_reassoc_nsz(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd reassoc nsz <4 x float> [[A:%.*]], [[B:%.*]]
+; CHECK-NEXT:     ret <4 x float> [[TMP1]]
+        %X = fadd reassoc nsz <4 x float> %A, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Y = fadd reassoc nsz <4 x float> %B, < float -1.000000e+00, float -2.000000e+00, float -3.000000e+00, float -4.000000e+00 >
+        %Z = fadd reassoc nsz <4 x float> %X, %Y
+        ret <4 x float> %Z
+}
+
+; ( A + C1 ) + ( B + -C1 )
+; Verify the fold is not done with only 'reassoc' ('nsz' is required).
+define <4 x float> @test_fadds_cancel_reassoc(<4 x float> %A, <4 x float> %B) {
+; CHECK-LABEL: @test_fadds_cancel_reassoc(
+; CHECK-NEXT:     [[TMP1:%.*]] = fadd reassoc <4 x float> [[A:%.*]], <float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00>
+; CHECK-NEXT:     [[TMP2:%.*]] = fadd reassoc <4 x float> [[B:%.*]], <float -1.000000e+00, float -2.000000e+00, float -3.000000e+00, float -4.000000e+00>
+; CHECK-NEXT:     [[TMP3:%.*]] = fadd reassoc <4 x float> [[TMP1]], [[TMP2]]
+; CHECK-NEXT:     ret <4 x float> [[TMP3]]
+        %X = fadd reassoc <4 x float> %A, < float 1.000000e+00, float 2.000000e+00, float 3.000000e+00, float 4.000000e+00 >
+        %Y = fadd reassoc <4 x float> %B, < float -1.000000e+00, float -2.000000e+00, float -3.000000e+00, float -4.000000e+00 >
+        %Z = fadd reassoc <4 x float> %X, %Y
+        ret <4 x float> %Z
+}