Index: lib/Transforms/InstCombine/InstCombineAddSub.cpp =================================================================== --- lib/Transforms/InstCombine/InstCombineAddSub.cpp +++ lib/Transforms/InstCombine/InstCombineAddSub.cpp @@ -1385,39 +1385,55 @@ // integer add followed by a promotion. if (SIToFPInst *LHSConv = dyn_cast(LHS)) { Value *LHSIntVal = LHSConv->getOperand(0); + Type *FPType = LHSConv->getType(); + + // TODO: This check is overly conservative. In many cases known bits + // analysis can tell us that the result of the addition has less significant + // bits than the integer type can hold. + auto IsValidPromotion = [](Type *FTy, Type *ITy) { + // Do we have enough bits in the significand to represent the result of + // the integer addition? + unsigned MaxRepresentableBits = + APFloat::semanticsPrecision(FTy->getFltSemantics()); + return ITy->getIntegerBitWidth() <= MaxRepresentableBits; + }; // (fadd double (sitofp x), fpcst) --> (sitofp (add int x, intcst)) // ... if the constant fits in the integer value. This is useful for things // like (double)(x & 1234) + 4.0 -> (double)((X & 1234)+4) which no longer // requires a constant pool load, and generally allows the add to be better // instcombined. - if (ConstantFP *CFP = dyn_cast(RHS)) { - Constant *CI = - ConstantExpr::getFPToSI(CFP, LHSIntVal->getType()); - if (LHSConv->hasOneUse() && - ConstantExpr::getSIToFP(CI, I.getType()) == CFP && - WillNotOverflowSignedAdd(LHSIntVal, CI, I)) { - // Insert the new integer add. - Value *NewAdd = Builder->CreateNSWAdd(LHSIntVal, - CI, "addconv"); - return new SIToFPInst(NewAdd, I.getType()); + if (ConstantFP *CFP = dyn_cast(RHS)) + if (IsValidPromotion(FPType, LHSIntVal->getType())) { + Constant *CI = + ConstantExpr::getFPToSI(CFP, LHSIntVal->getType()); + if (LHSConv->hasOneUse() && + ConstantExpr::getSIToFP(CI, I.getType()) == CFP && + WillNotOverflowSignedAdd(LHSIntVal, CI, I)) { + // Insert the new integer add. + Value *NewAdd = Builder->CreateNSWAdd(LHSIntVal, + CI, "addconv"); + return new SIToFPInst(NewAdd, I.getType()); + } } - } // (fadd double (sitofp x), (sitofp y)) --> (sitofp (add int x, y)) if (SIToFPInst *RHSConv = dyn_cast(RHS)) { Value *RHSIntVal = RHSConv->getOperand(0); - - // Only do this if x/y have the same type, if at least one of them has a - // single use (so we don't increase the number of int->fp conversions), - // and if the integer add will not overflow. - if (LHSIntVal->getType() == RHSIntVal->getType() && - (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && - WillNotOverflowSignedAdd(LHSIntVal, RHSIntVal, I)) { - // Insert the new integer add. - Value *NewAdd = Builder->CreateNSWAdd(LHSIntVal, - RHSIntVal, "addconv"); - return new SIToFPInst(NewAdd, I.getType()); + // It's enough to check LHS types only because we require int types to + // be the same for this transform. + if (IsValidPromotion(FPType, LHSIntVal->getType())) { + // Only do this if x/y have the same type, if at least one of them has a + // single use (so we don't increase the number of int->fp conversions), + // and if the integer add will not overflow. + if (LHSIntVal->getType() == RHSIntVal->getType() && + (LHSConv->hasOneUse() || RHSConv->hasOneUse()) && + WillNotOverflowSignedAdd(LHSIntVal, RHSIntVal, I)) { + // Insert the new integer add. + Value *NewAdd = Builder->CreateNSWAdd(LHSIntVal, + RHSIntVal, "addconv"); + return new SIToFPInst(NewAdd, I.getType()); + } } } } Index: test/Transforms/InstCombine/add-sitofp.ll =================================================================== --- test/Transforms/InstCombine/add-sitofp.ll +++ test/Transforms/InstCombine/add-sitofp.ll @@ -15,3 +15,88 @@ %p = fadd double %o, 1.0 ret double %p } + +define double @test(i32 %a) { +; CHECK-LABEL: @test( +; CHECK-NEXT: [[A_AND:%.*]] = and i32 [[A:%.*]], 1073741823 +; CHECK-NEXT: [[ADDCONV:%.*]] = add nuw nsw i32 [[A_AND]], 1 +; CHECK-NEXT: [[RES:%.*]] = sitofp i32 [[ADDCONV]] to double +; CHECK-NEXT: ret double [[RES]] +; + ; Drop two highest bits to guarantee that %a + 1 doesn't overflow + %a_and = and i32 %a, 1073741823 + %a_and_fp = sitofp i32 %a_and to double + %res = fadd double %a_and_fp, 1.0 + ret double %res +} + +define float @test_neg(i32 %a) { +; CHECK-LABEL: @test_neg( +; CHECK-NEXT: [[A_AND:%.*]] = and i32 [[A:%.*]], 1073741823 +; CHECK-NEXT: [[A_AND_FP:%.*]] = sitofp i32 [[A_AND]] to float +; CHECK-NEXT: [[RES:%.*]] = fadd float [[A_AND_FP]], 1.000000e+00 +; CHECK-NEXT: ret float [[RES]] +; + ; Drop two highest bits to guarantee that %a + 1 doesn't overflow + %a_and = and i32 %a, 1073741823 + %a_and_fp = sitofp i32 %a_and to float + %res = fadd float %a_and_fp, 1.0 + ret float %res +} + +define double @test_2(i32 %a, i32 %b) { +; CHECK-LABEL: @test_2( +; CHECK-NEXT: [[A_AND:%.*]] = and i32 [[A:%.*]], 1073741823 +; CHECK-NEXT: [[B_AND:%.*]] = and i32 [[B:%.*]], 1073741823 +; CHECK-NEXT: [[ADDCONV:%.*]] = add nuw nsw i32 [[A_AND]], [[B_AND]] +; CHECK-NEXT: [[RES:%.*]] = sitofp i32 [[ADDCONV]] to double +; CHECK-NEXT: ret double [[RES]] +; + ; Drop two highest bits to guarantee that %a + %b doesn't overflow + %a_and = and i32 %a, 1073741823 + %b_and = and i32 %b, 1073741823 + + %a_and_fp = sitofp i32 %a_and to double + %b_and_fp = sitofp i32 %b_and to double + + %res = fadd double %a_and_fp, %b_and_fp + ret double %res +} + +define float @test_2_neg(i32 %a, i32 %b) { +; CHECK-LABEL: @test_2_neg( +; CHECK-NEXT: [[A_AND:%.*]] = and i32 [[A:%.*]], 1073741823 +; CHECK-NEXT: [[B_AND:%.*]] = and i32 [[B:%.*]], 1073741823 +; CHECK-NEXT: [[A_AND_FP:%.*]] = sitofp i32 [[A_AND]] to float +; CHECK-NEXT: [[B_AND_FP:%.*]] = sitofp i32 [[B_AND]] to float +; CHECK-NEXT: [[RES:%.*]] = fadd float [[A_AND_FP]], [[B_AND_FP]] +; CHECK-NEXT: ret float [[RES]] +; + ; Drop two highest bits to guarantee that %a + %b doesn't overflow + %a_and = and i32 %a, 1073741823 + %b_and = and i32 %b, 1073741823 + + %a_and_fp = sitofp i32 %a_and to float + %b_and_fp = sitofp i32 %b_and to float + + %res = fadd float %a_and_fp, %b_and_fp + ret float %res +} + +; This test demonstrates overly conservative legality check. The float addition +; can be replaced with the integer addition because the result of the operation +; can be represented in float, but we don't do that now. +define float @test_3(i32 %a, i32 %b) { +; CHECK-LABEL: @test_3( +; CHECK-NEXT: [[M:%.*]] = lshr i32 [[A:%.*]], 24 +; CHECK-NEXT: [[N:%.*]] = and i32 [[M]], [[B:%.*]] +; CHECK-NEXT: [[O:%.*]] = sitofp i32 [[N]] to float +; CHECK-NEXT: [[P:%.*]] = fadd float [[O]], 1.000000e+00 +; CHECK-NEXT: ret float [[P]] +; + %m = lshr i32 %a, 24 + %n = and i32 %m, %b + %o = sitofp i32 %n to float + %p = fadd float %o, 1.0 + ret float %p +}