rdar://12801297

InstCombine for unsafe floating-point add/sub.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170471 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/InstCombine/fast-math.ll

@@ -28,6 +28,108 @@ define float @fold2(float %a) {
   ret float %mul1
 }
 
+; C * f1 + f1 = (C+1) * f1
+define double @fold3(double %f1) {
+  %t1 = fmul fast double 2.000000e+00, %f1
+  %t2 = fadd fast double %f1, %t1
+  ret double %t2
+; CHECK: @fold3
+; CHECK: fmul fast double %f1, 3.000000e+00
+}
+
+; (C1 - X) + (C2 - Y) => (C1+C2) - (X + Y)
+define float @fold4(float %f1, float %f2) {
+  %sub = fsub float 4.000000e+00, %f1
+  %sub1 = fsub float 5.000000e+00, %f2
+  %add = fadd fast float %sub, %sub1
+  ret float %add
+; CHECK: @fold4
+; CHECK: %1 = fadd fast float %f1, %f2
+; CHECK: fsub fast float 9.000000e+00, %1
+}
+
+; (X + C1) + C2 => X + (C1 + C2)
+define float @fold5(float %f1, float %f2) {
+  %add = fadd float %f1, 4.000000e+00
+  %add1 = fadd fast float %add, 5.000000e+00
+  ret float %add1
+; CHECK: @fold5
+; CHECK: fadd float %f1, 9.000000e+00
+}
+
+; (X + X) + X => 3.0 * X
+define float @fold6(float %f1) {
+  %t1 = fadd fast float %f1, %f1
+  %t2 = fadd fast float %f1, %t1
+  ret float %t2
+; CHECK: @fold6
+; CHECK: fmul fast float %f1, 3.000000e+00
+}
+
+; C1 * X + (X + X) = (C1 + 2) * X
+define float @fold7(float %f1) {
+  %t1 = fmul fast float %f1, 5.000000e+00
+  %t2 = fadd fast float %f1, %f1
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: @fold7
+; CHECK: fmul fast float %f1, 7.000000e+00
+}
+
+; (X + X) + (X + X) => 4.0 * X
+define float @fold8(float %f1) {
+  %t1 = fadd fast float %f1, %f1
+  %t2 = fadd fast float %f1, %f1
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: fold8
+; CHECK: fmul fast float %f1, 4.000000e+00
+}
+
+; X - (X + Y) => 0 - Y
+define float @fold9(float %f1, float %f2) {
+  %t1 = fadd float %f1, %f2
+  %t3 = fsub fast float %f1, %t1
+  ret float %t3
+
+; CHECK: @fold9
+; CHECK: fsub fast float 0.000000e+00, %f2
+}
+
+; Let C3 = C1 + C2. (f1 + C1) + (f2 + C2) => (f1 + f2) + C3 instead of
+; "(f1 + C3) + f2" or "(f2 + C3) + f1". Placing constant-addend at the 
+; top of resulting simplified expression tree may potentially reveal some
+; optimization opportunities in the super-expression trees.
+; 
+define float @fold10(float %f1, float %f2) {
+  %t1 = fadd fast float 2.000000e+00, %f1
+  %t2 = fsub fast float %f2, 3.000000e+00
+  %t3 = fadd fast float %t1, %t2
+  ret float %t3
+; CHECK: @fold10
+; CHECK: %t3 = fadd float %t2, -1.000000e+00
+; CHECK: ret float %t3
+}
+
+; once cause Crash/miscompilation
+define float @fail1(float %f1, float %f2) {
+  %conv3 = fadd fast float %f1, -1.000000e+00
+  %add = fadd fast float %conv3, %conv3
+  %add2 = fadd fast float %add, %conv3
+  ret float %add2
+; CHECK: @fail1
+; CHECK: ret
+}
+
+define double @fail2(double %f1, double %f2) {
+  %t1 = fsub fast double %f1, %f2
+  %t2 = fadd fast double %f1, %f2
+  %t3 = fsub fast double %t1, %t2
+  ret double %t3
+; CHECK: @fail2
+; CHECK: ret
+}
+
 ; rdar://12753946:  x * cond ? 1.0 : 0.0 => cond ? x : 0.0
 define double @select1(i32 %cond, double %x, double %y) {
   %tobool = icmp ne i32 %cond, 0