Particularly, it addresses cases where Reassociate breaks Subtracts but then fails to optimize combinations like I1 + -I2 where I1 and I2 have the same rank and are identical.
Patch by Dmitri Shtilman.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@219092
91177308-0d34-0410-b5e6-
96231b3b80d8
Value *X) {
unsigned XRank = Ops[i].Rank;
unsigned e = Ops.size();
Value *X) {
unsigned XRank = Ops[i].Rank;
unsigned e = Ops.size();
- for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j)
+ for (unsigned j = i+1; j != e && Ops[j].Rank == XRank; ++j) {
if (Ops[j].Op == X)
return j;
if (Ops[j].Op == X)
return j;
+ if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
+ if (Instruction *I2 = dyn_cast<Instruction>(X))
+ if (I1->isIdenticalTo(I2))
+ return j;
+ }
- for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j)
+ for (unsigned j = i-1; j != ~0U && Ops[j].Rank == XRank; --j) {
if (Ops[j].Op == X)
return j;
if (Ops[j].Op == X)
return j;
+ if (Instruction *I1 = dyn_cast<Instruction>(Ops[j].Op))
+ if (Instruction *I2 = dyn_cast<Instruction>(X))
+ if (I1->isIdenticalTo(I2))
+ return j;
+ }
--- /dev/null
+; RUN: opt < %s -reassociate -instcombine -S | FileCheck %s
+
+; Test that we can turn things like A*B + X - A*B -> X.
+
+define i32 @test1(i32 %a, i32 %b, i32 %x) {
+; CHECK-LABEL: test1
+; CHECK: ret i32 %x
+
+ %c = mul i32 %a, %b
+ %d = add i32 %c, %x
+ %c1 = mul i32 %a, %b
+ %f = sub i32 %d, %c1
+ ret i32 %f
+}
+