[llvm-commits] [llvm] r93369 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineAddSub.cpp test/Transforms/InstCombine/fsub-fadd.ll

[Bill Wendling]

Author: void
Date: Wed Jan 13 17:23:17 2010
New Revision: 93369

URL: http://llvm.org/viewvc/llvm-project?rev=93369&view=rev
Log:
When the visitSub method was split into visitSub and visitFSub, this xform was
added to the FSub version. However, the original version of this xform guarded
against doing this for floating point (!Op0->getType()->isFPOrFPVector()).

This is causing LLVM to perform incorrect xforms for code like:

void func(double *rhi, double *rlo, double xh, double xl, double yh, double yl){
  double mh, ml;
  double c = 134217729.0;
  double up, u1, u2, vp, v1, v2;
        
  up = xh*c;
  u1 = (xh - up) + up;
  u2 = xh - u1;
        
  vp = yh*c;
  v1 = (yh - vp) + vp;
  v2 = yh - v1;
        
  mh = xh*yh;
  ml = (((u1*v1 - mh) + (u1*v2)) + (u2*v1)) + (u2*v2);
  ml += xh*yl + xl*yh;
        
  *rhi = mh + ml;
  *rlo = (mh - (*rhi)) + ml;
}

The last line was optimized away, but rl is intended to be the difference
between the infinitely precise result of mh + ml and after it has been rounded
to double precision.

Added:
    llvm/trunk/test/Transforms/InstCombine/fsub-fadd.ll
Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp?rev=93369&r1=93368&r2=93369&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineAddSub.cpp Wed Jan 13 17:23:17 2010
@@ -736,16 +736,5 @@
   if (Value *V = dyn_castFNegVal(Op1))
     return BinaryOperator::CreateFAdd(Op0, V);
 
-  if (BinaryOperator *Op1I = dyn_cast<BinaryOperator>(Op1)) {
-    if (Op1I->getOpcode() == Instruction::FAdd) {
-      if (Op1I->getOperand(0) == Op0)              // X-(X+Y) == -Y
-        return BinaryOperator::CreateFNeg(Op1I->getOperand(1),
-                                          I.getName());
-      else if (Op1I->getOperand(1) == Op0)         // X-(Y+X) == -Y
-        return BinaryOperator::CreateFNeg(Op1I->getOperand(0),
-                                          I.getName());
-    }
-  }
-
   return 0;
 }

Added: llvm/trunk/test/Transforms/InstCombine/fsub-fadd.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fsub-fadd.ll?rev=93369&view=auto

==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fsub-fadd.ll (added)
+++ llvm/trunk/test/Transforms/InstCombine/fsub-fadd.ll Wed Jan 13 17:23:17 2010
@@ -0,0 +1,39 @@
+; RUN: opt < %s -instcombine -S | FileCheck %s
+; <rdar://problem/7530098>
+
+define void @func(double* %rhi, double* %rlo, double %xh, double %xl, double %yh, double %yl) nounwind ssp {
+entry:
+  %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
+  %tmp = fmul double %xh, 0x41A0000002000000      ; <double> [#uses=2]
+  %tmp1 = fsub double %xh, %tmp                   ; <double> [#uses=1]
+  %tmp2 = fadd double %tmp1, %tmp                 ; <double> [#uses=3]
+  %tmp3 = fsub double %xh, %tmp2                  ; <double> [#uses=2]
+  %tmp4 = fmul double %yh, 0x41A0000002000000     ; <double> [#uses=2]
+  %tmp5 = fsub double %yh, %tmp4                  ; <double> [#uses=1]
+  %tmp6 = fadd double %tmp5, %tmp4                ; <double> [#uses=3]
+  %tmp7 = fsub double %yh, %tmp6                  ; <double> [#uses=2]
+  %tmp8 = fmul double %xh, %yh                    ; <double> [#uses=3]
+  %tmp9 = fmul double %tmp2, %tmp6                ; <double> [#uses=1]
+  %tmp10 = fsub double %tmp9, %tmp8               ; <double> [#uses=1]
+  %tmp11 = fmul double %tmp2, %tmp7               ; <double> [#uses=1]
+  %tmp12 = fadd double %tmp10, %tmp11             ; <double> [#uses=1]
+  %tmp13 = fmul double %tmp3, %tmp6               ; <double> [#uses=1]
+  %tmp14 = fadd double %tmp12, %tmp13             ; <double> [#uses=1]
+  %tmp15 = fmul double %tmp3, %tmp7               ; <double> [#uses=1]
+  %tmp16 = fadd double %tmp14, %tmp15             ; <double> [#uses=1]
+  %tmp17 = fmul double %xh, %yl                   ; <double> [#uses=1]
+  %tmp18 = fmul double %xl, %yh                   ; <double> [#uses=1]
+  %tmp19 = fadd double %tmp17, %tmp18             ; <double> [#uses=1]
+  %tmp20 = fadd double %tmp19, %tmp16             ; <double> [#uses=2]
+  %tmp21 = fadd double %tmp8, %tmp20              ; <double> [#uses=1]
+  store double %tmp21, double* %rhi, align 8
+  %tmp22 = load double* %rhi, align 8             ; <double> [#uses=1]
+  %tmp23 = fsub double %tmp8, %tmp22              ; <double> [#uses=1]
+  %tmp24 = fadd double %tmp23, %tmp20             ; <double> [#uses=1]
+
+; CHECK: %tmp23 = fsub double %tmp8, %tmp21
+; CHECK: %tmp24 = fadd double %tmp23, %tmp20
+
+  store double %tmp24, double* %rlo, align 8
+  ret void
+}