Index: lib/Transforms/InstCombine/InstCombineCompares.cpp =================================================================== --- lib/Transforms/InstCombine/InstCombineCompares.cpp +++ lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -3173,6 +3173,19 @@ return Res; } + // (icmp sgt smin(PosA, B) 0) -> (icmp sgt B 0) + if (CI->isZero() && I.getPredicate() == ICmpInst::ICMP_SGT) + if (auto *SI = dyn_cast(Op0)) { + SelectPatternResult SPR = matchSelectPattern(SI, A, B); + if (SPR.Flavor == SPF_SMIN) { + if (isKnownNonNegative(A, DL) && isKnownNonZero(A, DL)) + return new ICmpInst(I.getPredicate(), B, CI); + if (isKnownNonNegative(B, DL) && isKnownNonZero(B, DL)) + return new ICmpInst(I.getPredicate(), A, CI); + } + } + + // The following transforms are only 'worth it' if the only user of the // subtraction is the icmp. if (Op0->hasOneUse()) { Index: test/Transforms/InstCombine/min-positive.ll =================================================================== --- test/Transforms/InstCombine/min-positive.ll +++ test/Transforms/InstCombine/min-positive.ll @@ -0,0 +1,34 @@ +; RUN: opt -S -instcombine < %s | FileCheck %s + +@g = external global i32 + +define i1 @test(i32 %other) { +; CHECK-LABEL: @test +; CHECK: %test = icmp sgt i32 %other, 0 + %positive = load i32, i32* @g, !range !{i32 1, i32 2048} + %cmp = icmp slt i32 %positive, %other + %sel = select i1 %cmp, i32 %positive, i32 %other + %test = icmp sgt i32 %sel, 0 + ret i1 %test +} + +define i1 @test2(i32 %other) { +; CHECK-LABEL: @test2 +; CHECK: %test = icmp sgt i32 %other, 0 + %positive = load i32, i32* @g, !range !{i32 1, i32 2048} + %cmp = icmp slt i32 %other, %positive + %sel = select i1 %cmp, i32 %other, i32 %positive + %test = icmp sgt i32 %sel, 0 + ret i1 %test +} + +; %positive might be zero +define i1 @test3(i32 %other) { +; CHECK-LABEL: @test3 +; CHECK: %test = icmp sgt i32 %sel, 0 + %positive = load i32, i32* @g, !range !{i32 0, i32 2048} + %cmp = icmp slt i32 %positive, %other + %sel = select i1 %cmp, i32 %positive, i32 %other + %test = icmp sgt i32 %sel, 0 + ret i1 %test +}