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author | Antonio Frighetto <me@antoniofrighetto.com> | 2024-06-15 10:45:32 +0200 |
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committer | Antonio Frighetto <me@antoniofrighetto.com> | 2024-06-17 19:34:48 +0200 |
commit | a4b44c003e35bb6ed78af6300e576554d41f0368 (patch) | |
tree | 0bf375b35feecb603b8b4d4184acb38e6ebd580a | |
parent | 3ad31e12ccfc7db25f3cbedc4ee966e7099ac78f (diff) | |
download | llvm-a4b44c003e35bb6ed78af6300e576554d41f0368.zip llvm-a4b44c003e35bb6ed78af6300e576554d41f0368.tar.gz llvm-a4b44c003e35bb6ed78af6300e576554d41f0368.tar.bz2 |
[InstCombine] Canonicalize `icmp ult (add X, C2), C` expressions
`icmp ult (add X, C2), C` can be folded to `icmp ne (and X, C), 2C`,
subject to `C == -C2` and C2 being a power of 2.
Proofs: https://alive2.llvm.org/ce/z/P-VVmQ.
Fixes: https://github.com/llvm/llvm-project/issues/75613.
-rw-r--r-- | llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp | 7 | ||||
-rw-r--r-- | llvm/test/Transforms/InstCombine/icmp-add.ll | 78 |
2 files changed, 85 insertions, 0 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp index 34b0f8b..522c31f 100644 --- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3130,6 +3130,13 @@ Instruction *InstCombinerImpl::foldICmpAddConstant(ICmpInst &Cmp, return new ICmpInst(ICmpInst::ICMP_EQ, Builder.CreateAnd(X, -C), ConstantExpr::getNeg(cast<Constant>(Y))); + // X+C2 <u C -> (X & C) == 2C + // iff C == -(C2) + // C2 is a power of 2 + if (Pred == ICmpInst::ICMP_ULT && C2->isPowerOf2() && C == -*C2) + return new ICmpInst(ICmpInst::ICMP_NE, Builder.CreateAnd(X, C), + ConstantInt::get(Ty, C * 2)); + // X+C >u C2 -> (X & ~C2) != C // iff C & C2 == 0 // C2+1 is a power of 2 diff --git a/llvm/test/Transforms/InstCombine/icmp-add.ll b/llvm/test/Transforms/InstCombine/icmp-add.ll index 6b4e5a53..baa6f3d 100644 --- a/llvm/test/Transforms/InstCombine/icmp-add.ll +++ b/llvm/test/Transforms/InstCombine/icmp-add.ll @@ -3023,4 +3023,82 @@ define i1 @icmp_addnuw_nonzero_fail_multiuse(i32 %x, i32 %y) { ret i1 %c } +define i1 @ult_add_C2_pow2_C_neg(i8 %x) { +; CHECK-LABEL: @ult_add_C2_pow2_C_neg( +; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X:%.*]], -32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[TMP1]], -64 +; CHECK-NEXT: ret i1 [[C]] +; + %i = add i8 %x, 32 + %c = icmp ult i8 %i, -32 + ret i1 %c +} + +define i1 @ult_add_nsw_C2_pow2_C_neg(i8 %x) { +; CHECK-LABEL: @ult_add_nsw_C2_pow2_C_neg( +; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X:%.*]], -32 +; CHECK-NEXT: [[C:%.*]] = icmp ne i8 [[TMP1]], -64 +; CHECK-NEXT: ret i1 [[C]] +; + %i = add nsw i8 %x, 32 + %c = icmp ult i8 %i, -32 + ret i1 %c +} + +define i1 @ult_add_nuw_nsw_C2_pow2_C_neg(i8 %x) { +; CHECK-LABEL: @ult_add_nuw_nsw_C2_pow2_C_neg( +; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[X:%.*]], -64 +; CHECK-NEXT: ret i1 [[C]] +; + %i = add nuw nsw i8 %x, 32 + %c = icmp ult i8 %i, -32 + ret i1 %c +} + +define i1 @ult_add_C2_neg_C_pow2(i8 %x) { +; CHECK-LABEL: @ult_add_C2_neg_C_pow2( +; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X:%.*]], -32 +; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[TMP1]], 32 +; CHECK-NEXT: ret i1 [[C]] +; + %i = add i8 %x, -32 + %c = icmp ult i8 %i, 32 + ret i1 %c +} + +define <2 x i1> @ult_add_C2_pow2_C_neg_vec(<2 x i8> %x) { +; CHECK-LABEL: @ult_add_C2_pow2_C_neg_vec( +; CHECK-NEXT: [[TMP1:%.*]] = and <2 x i8> [[X:%.*]], <i8 -32, i8 -32> +; CHECK-NEXT: [[C:%.*]] = icmp ne <2 x i8> [[TMP1]], <i8 -64, i8 -64> +; CHECK-NEXT: ret <2 x i1> [[C]] +; + %i = add <2 x i8> %x, <i8 32, i8 32> + %c = icmp ult <2 x i8> %i, <i8 -32, i8 -32> + ret <2 x i1> %c +} + +define i1 @ult_add_C2_pow2_C_neg_multiuse(i8 %x) { +; CHECK-LABEL: @ult_add_C2_pow2_C_neg_multiuse( +; CHECK-NEXT: [[I:%.*]] = add i8 [[X:%.*]], 32 +; CHECK-NEXT: [[C:%.*]] = icmp ult i8 [[I]], -32 +; CHECK-NEXT: call void @use(i8 [[I]]) +; CHECK-NEXT: ret i1 [[C]] +; + %i = add i8 %x, 32 + %c = icmp ult i8 %i, -32 + call void @use(i8 %i) + ret i1 %c +} + +define i1 @uge_add_C2_pow2_C_neg(i8 %x) { +; CHECK-LABEL: @uge_add_C2_pow2_C_neg( +; CHECK-NEXT: [[TMP1:%.*]] = and i8 [[X:%.*]], -32 +; CHECK-NEXT: [[C:%.*]] = icmp eq i8 [[TMP1]], -64 +; CHECK-NEXT: ret i1 [[C]] +; + %i = add i8 %x, 32 + %c = icmp uge i8 %i, -32 + ret i1 %c +} + declare void @llvm.assume(i1) |