[llvm-commits] [llvm] r132185 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineSelect.cpp test/Transforms/InstCombine/select.ll
Benjamin Kramer
benny.kra at googlemail.com
Fri May 27 06:00:16 PDT 2011
Author: d0k
Date: Fri May 27 08:00:16 2011
New Revision: 132185
URL: http://llvm.org/viewvc/llvm-project?rev=132185&view=rev
Log:
InstCombine: Make switch folding with equality compares more aggressive by trying instsimplify on the arm where we know the compared value.
Stuff like "x == y ? y : x&y" now folds into "x&y".
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
llvm/trunk/test/Transforms/InstCombine/select.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp?rev=132185&r1=132184&r2=132185&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineSelect.cpp Fri May 27 08:00:16 2011
@@ -278,6 +278,49 @@
return 0;
}
+/// SimplifyWithOpReplaced - See if V simplifies when its operand Op is
+/// replaced with RepOp.
+static Value *SimplifyWithOpReplaced(Value *V, Value *Op, Value *RepOp,
+ const TargetData *TD) {
+ // Trivial replacement.
+ if (V == Op)
+ return RepOp;
+
+ Instruction *I = dyn_cast<Instruction>(V);
+ if (!I)
+ return 0;
+
+ // If this is a binary operator, try to simplify it with the replaced op.
+ if (BinaryOperator *B = dyn_cast<BinaryOperator>(I)) {
+ if (B->getOperand(0) == Op)
+ return SimplifyBinOp(B->getOpcode(), RepOp, B->getOperand(1), TD);
+ if (B->getOperand(1) == Op)
+ return SimplifyBinOp(B->getOpcode(), B->getOperand(0), RepOp, TD);
+ }
+
+ // If all operands are constant after substituting Op for RepOp then we can
+ // constant fold the instruction.
+ if (Constant *CRepOp = dyn_cast<Constant>(RepOp)) {
+ // Build a list of all constant operands.
+ SmallVector<Constant*, 8> ConstOps;
+ for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
+ if (I->getOperand(i) == Op)
+ ConstOps.push_back(CRepOp);
+ else if (Constant *COp = dyn_cast<Constant>(I->getOperand(i)))
+ ConstOps.push_back(COp);
+ else
+ break;
+ }
+
+ // All operands were constants, fold it.
+ if (ConstOps.size() == I->getNumOperands())
+ return ConstantFoldInstOperands(I->getOpcode(), I->getType(),
+ ConstOps.data(), ConstOps.size(), TD);
+ }
+
+ return 0;
+}
+
/// visitSelectInstWithICmp - Visit a SelectInst that has an
/// ICmpInst as its first operand.
///
@@ -416,25 +459,21 @@
}
}
- if (CmpLHS == TrueVal && CmpRHS == FalseVal) {
- // Transform (X == Y) ? X : Y -> Y
- if (Pred == ICmpInst::ICMP_EQ)
+ // If we have an equality comparison then we know the value in one of the
+ // arms of the select. See if substituting this value into the arm and
+ // simplifying the result yields the same value as the other arm.
+ if (Pred == ICmpInst::ICMP_EQ) {
+ if (SimplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, TD) == TrueVal ||
+ SimplifyWithOpReplaced(FalseVal, CmpRHS, CmpLHS, TD) == TrueVal)
return ReplaceInstUsesWith(SI, FalseVal);
- // Transform (X != Y) ? X : Y -> X
- if (Pred == ICmpInst::ICMP_NE)
+ } else if (Pred == ICmpInst::ICMP_NE) {
+ if (SimplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, TD) == FalseVal ||
+ SimplifyWithOpReplaced(TrueVal, CmpRHS, CmpLHS, TD) == FalseVal)
return ReplaceInstUsesWith(SI, TrueVal);
- /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
-
- } else if (CmpLHS == FalseVal && CmpRHS == TrueVal) {
- // Transform (X == Y) ? Y : X -> X
- if (Pred == ICmpInst::ICMP_EQ)
- return ReplaceInstUsesWith(SI, FalseVal);
- // Transform (X != Y) ? Y : X -> Y
- if (Pred == ICmpInst::ICMP_NE)
- return ReplaceInstUsesWith(SI, TrueVal);
- /// NOTE: if we wanted to, this is where to detect integer MIN/MAX
}
+ // NOTE: if we wanted to, this is where to detect integer MIN/MAX
+
if (isa<Constant>(CmpRHS)) {
if (CmpLHS == TrueVal && Pred == ICmpInst::ICMP_EQ) {
// Transform (X == C) ? X : Y -> (X == C) ? C : Y
Modified: llvm/trunk/test/Transforms/InstCombine/select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/select.ll?rev=132185&r1=132184&r2=132185&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/select.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/select.ll Fri May 27 08:00:16 2011
@@ -749,3 +749,43 @@
; CHECK: icmp eq
; CHECK: ret i1
}
+
+define i32 @test56(i16 %x) nounwind {
+ %tobool = icmp eq i16 %x, 0
+ %conv = zext i16 %x to i32
+ %cond = select i1 %tobool, i32 0, i32 %conv
+ ret i32 %cond
+; CHECK: @test56
+; CHECK-NEXT: zext
+; CHECK-NEXT: ret
+}
+
+define i32 @test57(i32 %x, i32 %y) nounwind {
+ %and = and i32 %x, %y
+ %tobool = icmp eq i32 %x, 0
+ %.and = select i1 %tobool, i32 0, i32 %and
+ ret i32 %.and
+; CHECK: @test57
+; CHECK-NEXT: and i32 %x, %y
+; CHECK-NEXT: ret
+}
+
+define i32 @test58(i16 %x) nounwind {
+ %tobool = icmp ne i16 %x, 1
+ %conv = zext i16 %x to i32
+ %cond = select i1 %tobool, i32 %conv, i32 1
+ ret i32 %cond
+; CHECK: @test58
+; CHECK-NEXT: zext
+; CHECK-NEXT: ret
+}
+
+define i32 @test59(i32 %x, i32 %y) nounwind {
+ %and = and i32 %x, %y
+ %tobool = icmp ne i32 %x, %y
+ %.and = select i1 %tobool, i32 %and, i32 %y
+ ret i32 %.and
+; CHECK: @test59
+; CHECK-NEXT: and i32 %x, %y
+; CHECK-NEXT: ret
+}
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