Index: llvm/lib/Analysis/ValueTracking.cpp =================================================================== --- llvm/lib/Analysis/ValueTracking.cpp +++ llvm/lib/Analysis/ValueTracking.cpp @@ -5653,6 +5653,41 @@ } } +static void setLimitsForSelect(const SelectInst &SI, APInt &Lower, + APInt &Upper) { + // Don't bother if we don't have a constant operand. + if (!isa(SI.getTrueValue()) && !isa(SI.getFalseValue())) + return; + + const Value *LHS, *RHS; + SelectPatternResult R = matchSelectPattern(&SI, LHS, RHS); + if (R.Flavor == SPF_UNKNOWN) + return; + + const APInt *C; + if (!match(LHS, m_APInt(C)) && !match(RHS, m_APInt(C))) + return; + + switch (R.Flavor) { + case SPF_UMIN: + Upper = *C + 1; + break; + case SPF_UMAX: + Lower = *C; + break; + case SPF_SMIN: + Lower = APInt::getSignedMinValue(C->getBitWidth()); + Upper = *C + 1; + break; + case SPF_SMAX: + Lower = *C; + Upper = APInt::getSignedMaxValue(C->getBitWidth()) + 1; + break; + default: + break; + } +} + ConstantRange llvm::computeConstantRange(const Value *V, bool UseInstrInfo) { assert(V->getType()->isIntOrIntVectorTy() && "Expected integer instruction"); @@ -5664,6 +5699,8 @@ setLimitsForBinOp(*BO, Lower, Upper, IIQ); else if (auto *II = dyn_cast(V)) setLimitsForIntrinsic(*II, Lower, Upper); + else if (auto *SI = dyn_cast(V)) + setLimitsForSelect(*SI, Lower, Upper); ConstantRange CR = Lower != Upper ? ConstantRange(Lower, Upper) : ConstantRange(BitWidth, true); Index: llvm/test/Transforms/InstCombine/minmax-fold.ll =================================================================== --- llvm/test/Transforms/InstCombine/minmax-fold.ll +++ llvm/test/Transforms/InstCombine/minmax-fold.ll @@ -533,6 +533,37 @@ ret i32 %res } +; Check that there is no infinite loop because of reverse cmp transformation: +; (icmp slt smax(PositiveA, B) 2) -> (icmp eq B 1) +define i32 @clamp_check_for_no_infinite_loop3(i32 %i) { +; CHECK-LABEL: @clamp_check_for_no_infinite_loop3( +; CHECK-NEXT: [[I2:%.*]] = icmp sgt i32 [[I:%.*]], 1 +; CHECK-NEXT: [[I3:%.*]] = select i1 [[I2]], i32 [[I]], i32 1 +; CHECK-NEXT: br i1 true, label [[TRUELABEL:%.*]], label [[FALSELABEL:%.*]] +; CHECK: truelabel: +; CHECK-NEXT: [[I5:%.*]] = icmp slt i32 [[I3]], 2 +; CHECK-NEXT: [[I6:%.*]] = select i1 [[I5]], i32 [[I3]], i32 2 +; CHECK-NEXT: [[I7:%.*]] = shl nuw nsw i32 [[I6]], 2 +; CHECK-NEXT: ret i32 [[I7]] +; CHECK: falselabel: +; CHECK-NEXT: ret i32 0 +; + + %i2 = icmp sgt i32 %i, 1 + %i3 = select i1 %i2, i32 %i, i32 1 + %i4 = icmp sgt i32 %i3, 0 + br i1 %i4, label %truelabel, label %falselabel + +truelabel: ; %i<=1, %i3>0 + %i5 = icmp slt i32 %i3, 2 + %i6 = select i1 %i5, i32 %i3, i32 2 + %i7 = shl nuw nsw i32 %i6, 2 + ret i32 %i7 + +falselabel: + ret i32 0 +} + ; The next 3 min tests should canonicalize to the same form...and not infinite loop. define double @PR31751_umin1(i32 %x) { Index: llvm/test/Transforms/InstSimplify/cmp_of_min_max.ll =================================================================== --- llvm/test/Transforms/InstSimplify/cmp_of_min_max.ll +++ llvm/test/Transforms/InstSimplify/cmp_of_min_max.ll @@ -3,10 +3,7 @@ define i1 @test_umin1(i32 %n) { ; CHECK-LABEL: @test_umin1( -; CHECK-NEXT: [[C1:%.*]] = icmp ugt i32 [[N:%.*]], 10 -; CHECK-NEXT: [[S:%.*]] = select i1 [[C1]], i32 [[N]], i32 10 -; CHECK-NEXT: [[C2:%.*]] = icmp ugt i32 [[S]], 9 -; CHECK-NEXT: ret i1 [[C2]] +; CHECK-NEXT: ret i1 true ; %c1 = icmp ugt i32 %n, 10 %s = select i1 %c1, i32 %n, i32 10 @@ -40,10 +37,7 @@ define i1 @test_umax1(i32 %n) { ; CHECK-LABEL: @test_umax1( -; CHECK-NEXT: [[C1:%.*]] = icmp ult i32 [[N:%.*]], 10 -; CHECK-NEXT: [[S:%.*]] = select i1 [[C1]], i32 [[N]], i32 10 -; CHECK-NEXT: [[C2:%.*]] = icmp ult i32 [[S]], 11 -; CHECK-NEXT: ret i1 [[C2]] +; CHECK-NEXT: ret i1 true ; %c1 = icmp ult i32 %n, 10 %s = select i1 %c1, i32 %n, i32 10 @@ -77,10 +71,7 @@ define i1 @test_smin1(i32 %n) { ; CHECK-LABEL: @test_smin1( -; CHECK-NEXT: [[C1:%.*]] = icmp sgt i32 [[N:%.*]], -10 -; CHECK-NEXT: [[S:%.*]] = select i1 [[C1]], i32 [[N]], i32 -10 -; CHECK-NEXT: [[C2:%.*]] = icmp sgt i32 [[S]], -11 -; CHECK-NEXT: ret i1 [[C2]] +; CHECK-NEXT: ret i1 true ; %c1 = icmp sgt i32 %n, -10 %s = select i1 %c1, i32 %n, i32 -10 @@ -114,10 +105,7 @@ define i1 @test_smax1(i32 %n) { ; CHECK-LABEL: @test_smax1( -; CHECK-NEXT: [[C1:%.*]] = icmp slt i32 [[N:%.*]], 10 -; CHECK-NEXT: [[S:%.*]] = select i1 [[C1]], i32 [[N]], i32 10 -; CHECK-NEXT: [[C2:%.*]] = icmp slt i32 [[S]], 11 -; CHECK-NEXT: ret i1 [[C2]] +; CHECK-NEXT: ret i1 true ; %c1 = icmp slt i32 %n, 10 %s = select i1 %c1, i32 %n, i32 10