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fix fmls fp16
Tim Northover remarked that the added patterns for fmls fp16
produce wrong code in case the fsub instruction has a
multiplication as its first operand, i.e., all the patterns FMLSv*_OP1:
> define <8 x half> @test_FMLSv8f16_OP1(<8 x half> %a, <8 x half> %b, <8 x half> %c) {
> ; CHECK-LABEL: test_FMLSv8f16_OP1:
> ; CHECK: fmls {{v[0-9]+}}.8h, {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
> entry:
>
> %mul = fmul fast <8 x half> %c, %b
> %sub = fsub fast <8 x half> %mul, %a
> ret <8 x half> %sub
> }
>
> This doesn't look right to me. The exact instruction produced is "fmls
> v0.8h, v2.8h, v1.8h", which I think calculates "v0 - v2*v1", but the
> IR is calculating "v2*v1-v0". The equivalent <4 x float> code also
> doesn't emit an fmls.
This patch generates an fmla and negates the value of the operand2 of the fsub.
Inspecting the pattern match, I found that there was another mistake in the
opcode to be selected: matching FMULv4*16 should generate FMLSv4*16
and not FMLSv2*32.
Tested on aarch64-linux with make check-all.
Differential Revision: https://reviews.llvm.org/D67990
llvm-svn: 374044
This commit is contained in:
Sebastian Pop
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@ -80,6 +80,7 @@ enum class MachineCombinerPattern {
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FMLAv4i32_indexed_OP2,
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FMLSv1i32_indexed_OP2,
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FMLSv1i64_indexed_OP2,
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FMLSv4f16_OP1,
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FMLSv4f16_OP2,
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FMLSv8f16_OP1,
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FMLSv8f16_OP2,
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@ -87,6 +88,7 @@ enum class MachineCombinerPattern {
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FMLSv2f32_OP2,
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FMLSv2f64_OP1,
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FMLSv2f64_OP2,
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FMLSv4i16_indexed_OP1,
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FMLSv4i16_indexed_OP2,
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FMLSv8i16_indexed_OP1,
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FMLSv8i16_indexed_OP2,
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@ -3806,8 +3806,8 @@ static bool getFMAPatterns(MachineInstr &Root,
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Found |= Match(AArch64::FMULv4i16_indexed, 2, MCP::FMLSv4i16_indexed_OP2) ||
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Match(AArch64::FMULv4f16, 2, MCP::FMLSv4f16_OP2);
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Found |= Match(AArch64::FMULv4i16_indexed, 1, MCP::FMLSv2i32_indexed_OP1) ||
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Match(AArch64::FMULv4f16, 1, MCP::FMLSv2f32_OP1);
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Found |= Match(AArch64::FMULv4i16_indexed, 1, MCP::FMLSv4i16_indexed_OP1) ||
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Match(AArch64::FMULv4f16, 1, MCP::FMLSv4f16_OP1);
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break;
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case AArch64::FSUBv8f16:
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Found |= Match(AArch64::FMULv8i16_indexed, 2, MCP::FMLSv8i16_indexed_OP2) ||
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@ -3888,6 +3888,7 @@ bool AArch64InstrInfo::isThroughputPattern(
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case MachineCombinerPattern::FMLAv4f32_OP2:
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case MachineCombinerPattern::FMLAv4i32_indexed_OP1:
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case MachineCombinerPattern::FMLAv4i32_indexed_OP2:
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case MachineCombinerPattern::FMLSv4i16_indexed_OP1:
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case MachineCombinerPattern::FMLSv4i16_indexed_OP2:
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case MachineCombinerPattern::FMLSv8i16_indexed_OP1:
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case MachineCombinerPattern::FMLSv8i16_indexed_OP2:
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@ -3895,6 +3896,7 @@ bool AArch64InstrInfo::isThroughputPattern(
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case MachineCombinerPattern::FMLSv1i64_indexed_OP2:
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case MachineCombinerPattern::FMLSv2i32_indexed_OP2:
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case MachineCombinerPattern::FMLSv2i64_indexed_OP2:
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case MachineCombinerPattern::FMLSv4f16_OP1:
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case MachineCombinerPattern::FMLSv4f16_OP2:
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case MachineCombinerPattern::FMLSv8f16_OP1:
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case MachineCombinerPattern::FMLSv8f16_OP2:
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@ -4497,6 +4499,26 @@ void AArch64InstrInfo::genAlternativeCodeSequence(
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FMAInstKind::Indexed);
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break;
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case MachineCombinerPattern::FMLSv4f16_OP1:
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case MachineCombinerPattern::FMLSv4i16_indexed_OP1: {
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RC = &AArch64::FPR64RegClass;
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Register NewVR = MRI.createVirtualRegister(RC);
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MachineInstrBuilder MIB1 =
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BuildMI(MF, Root.getDebugLoc(), TII->get(AArch64::FNEGv4f16), NewVR)
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.add(Root.getOperand(2));
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InsInstrs.push_back(MIB1);
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InstrIdxForVirtReg.insert(std::make_pair(NewVR, 0));
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if (Pattern == MachineCombinerPattern::FMLSv4f16_OP1) {
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Opc = AArch64::FMLAv4f16;
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MUL = genFusedMultiply(MF, MRI, TII, Root, InsInstrs, 1, Opc, RC,
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FMAInstKind::Accumulator, &NewVR);
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} else {
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Opc = AArch64::FMLAv4i16_indexed;
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MUL = genFusedMultiply(MF, MRI, TII, Root, InsInstrs, 1, Opc, RC,
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FMAInstKind::Indexed, &NewVR);
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}
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break;
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}
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case MachineCombinerPattern::FMLSv4f16_OP2:
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RC = &AArch64::FPR64RegClass;
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Opc = AArch64::FMLSv4f16;
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@ -4525,18 +4547,25 @@ void AArch64InstrInfo::genAlternativeCodeSequence(
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break;
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case MachineCombinerPattern::FMLSv8f16_OP1:
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case MachineCombinerPattern::FMLSv8i16_indexed_OP1: {
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RC = &AArch64::FPR128RegClass;
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Opc = AArch64::FMLSv8f16;
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MUL = genFusedMultiply(MF, MRI, TII, Root, InsInstrs, 1, Opc, RC,
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FMAInstKind::Accumulator);
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Register NewVR = MRI.createVirtualRegister(RC);
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MachineInstrBuilder MIB1 =
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BuildMI(MF, Root.getDebugLoc(), TII->get(AArch64::FNEGv8f16), NewVR)
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.add(Root.getOperand(2));
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InsInstrs.push_back(MIB1);
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InstrIdxForVirtReg.insert(std::make_pair(NewVR, 0));
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if (Pattern == MachineCombinerPattern::FMLSv8f16_OP1) {
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Opc = AArch64::FMLAv8f16;
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MUL = genFusedMultiply(MF, MRI, TII, Root, InsInstrs, 1, Opc, RC,
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FMAInstKind::Accumulator, &NewVR);
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} else {
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Opc = AArch64::FMLAv8i16_indexed;
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MUL = genFusedMultiply(MF, MRI, TII, Root, InsInstrs, 1, Opc, RC,
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FMAInstKind::Indexed, &NewVR);
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}
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break;
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case MachineCombinerPattern::FMLSv8i16_indexed_OP1:
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RC = &AArch64::FPR128RegClass;
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Opc = AArch64::FMLSv8i16_indexed;
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MUL = genFusedMultiply(MF, MRI, TII, Root, InsInstrs, 1, Opc, RC,
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FMAInstKind::Indexed);
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break;
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}
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case MachineCombinerPattern::FMLSv8f16_OP2:
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RC = &AArch64::FPR128RegClass;
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Opc = AArch64::FMLSv8f16;
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@ -138,6 +138,16 @@ entry:
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ret <8 x half> %add
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}
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define <4 x half> @test_FMLSv4f16_OP1(<4 x half> %a, <4 x half> %b, <4 x half> %c) {
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; CHECK-LABEL: test_FMLSv4f16_OP1:
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; CHECK: fneg {{v[0-9]+}}.4h, {{v[0-9]+}}.4h
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; CHECK: fmla {{v[0-9]+}}.4h, {{v[0-9]+}}.4h, {{v[0-9]+}}.4h
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entry:
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%mul = fmul fast <4 x half> %c, %b
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%sub = fsub fast <4 x half> %mul, %a
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ret <4 x half> %sub
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}
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define <4 x half> @test_FMLSv4f16_OP2(<4 x half> %a, <4 x half> %b, <4 x half> %c) {
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; CHECK-LABEL: test_FMLSv4f16_OP2:
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; CHECK: fmls {{v[0-9]+}}.4h, {{v[0-9]+}}.4h, {{v[0-9]+}}.4h
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@ -149,7 +159,8 @@ entry:
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define <8 x half> @test_FMLSv8f16_OP1(<8 x half> %a, <8 x half> %b, <8 x half> %c) {
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; CHECK-LABEL: test_FMLSv8f16_OP1:
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; CHECK: fmls {{v[0-9]+}}.8h, {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
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; CHECK: fneg {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
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; CHECK: fmla {{v[0-9]+}}.8h, {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
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entry:
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%mul = fmul fast <8 x half> %c, %b
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%sub = fsub fast <8 x half> %mul, %a
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@ -185,7 +196,8 @@ define <8 x half> @test_FMLSv8i16_indexed_OP1(<8 x half> %a, <8 x i16> %b, <8 x
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; CHECK: mul
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; CHECK: fsub
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; CHECK-FIXME: It should instead produce the following instruction:
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; CHECK-FIXME: fmls {{v[0-9]+}}.8h, {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
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; CHECK-FIXME: fneg {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
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; CHECK-FIXME: fmla {{v[0-9]+}}.8h, {{v[0-9]+}}.8h, {{v[0-9]+}}.8h
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entry:
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%mul = mul <8 x i16> %c, %b
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%m = bitcast <8 x i16> %mul to <8 x half>
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