In a few places in getInstrMapping, we check if use/def instructions for the
instruction we're mapping have floating point constraints.
We can improve this check and reduce the number of copies in GISel-compiled code
if we make a couple observations:
- For a def instruction, it only matters if the def instruction must always
output a value stored on a FPR
- For a use instruction, it only matters if the use instruction must always
only take in values stored in FPRs
This adds two new functions:
- onlyUsesFP
- onlyDefinesFP
Then we can use those when we're checking the uses/defs instead.
Without this patch, the load, unmerge, store, and select in the added test
would have unnecessary copies.
Differential Revision: https://reviews.llvm.org/D62426
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@361679
91177308-0d34-0410-b5e6-
96231b3b80d8
&AArch64::FPRRegBank;
}
+bool AArch64RegisterBankInfo::onlyUsesFP(const MachineInstr &MI,
+ const MachineRegisterInfo &MRI,
+ const TargetRegisterInfo &TRI) const {
+ switch (MI.getOpcode()) {
+ case TargetOpcode::G_FPTOSI:
+ case TargetOpcode::G_FPTOUI:
+ case TargetOpcode::G_FCMP:
+ return true;
+ default:
+ break;
+ }
+ return hasFPConstraints(MI, MRI, TRI);
+}
+
+bool AArch64RegisterBankInfo::onlyDefinesFP(
+ const MachineInstr &MI, const MachineRegisterInfo &MRI,
+ const TargetRegisterInfo &TRI) const {
+ switch (MI.getOpcode()) {
+ case TargetOpcode::G_SITOFP:
+ case TargetOpcode::G_UITOFP:
+ case TargetOpcode::G_EXTRACT_VECTOR_ELT:
+ case TargetOpcode::G_INSERT_VECTOR_ELT:
+ return true;
+ default:
+ break;
+ }
+ return hasFPConstraints(MI, MRI, TRI);
+}
+
const RegisterBankInfo::InstructionMapping &
AArch64RegisterBankInfo::getInstrMapping(const MachineInstr &MI) const {
const unsigned Opc = MI.getOpcode();
// assume this was a floating point load in the IR.
// If it was not, we would have had a bitcast before
// reaching that instruction.
- if (hasFPConstraints(UseMI, MRI, TRI)) {
+ if (onlyUsesFP(UseMI, MRI, TRI)) {
OpRegBankIdx[0] = PMI_FirstFPR;
break;
}
if (!VReg)
break;
MachineInstr *DefMI = MRI.getVRegDef(VReg);
- if (hasFPConstraints(*DefMI, MRI, TRI))
+ if (onlyDefinesFP(*DefMI, MRI, TRI))
OpRegBankIdx[0] = PMI_FirstFPR;
break;
}
// fpr = G_FOO %z ...
if (any_of(
MRI.use_instructions(MI.getOperand(0).getReg()),
- [&](MachineInstr &MI) { return hasFPConstraints(MI, MRI, TRI); }))
+ [&](MachineInstr &MI) { return onlyUsesFP(MI, MRI, TRI); }))
++NumFP;
// Check if the defs of the source values always produce floating point
unsigned VReg = MI.getOperand(Idx).getReg();
MachineInstr *DefMI = MRI.getVRegDef(VReg);
if (getRegBank(VReg, MRI, TRI) == &AArch64::FPRRegBank ||
- hasFPConstraints(*DefMI, MRI, TRI))
+ onlyDefinesFP(*DefMI, MRI, TRI))
++NumFP;
}
// UNMERGE into scalars from a vector should always use FPR.
// Likewise if any of the uses are FP instructions.
if (SrcTy.isVector() ||
- any_of(
- MRI.use_instructions(MI.getOperand(0).getReg()),
- [&](MachineInstr &MI) { return hasFPConstraints(MI, MRI, TRI); })) {
+ any_of(MRI.use_instructions(MI.getOperand(0).getReg()),
+ [&](MachineInstr &MI) { return onlyUsesFP(MI, MRI, TRI); })) {
// Set the register bank of every operand to FPR.
for (unsigned Idx = 0, NumOperands = MI.getNumOperands();
Idx < NumOperands; ++Idx)
bool hasFPConstraints(const MachineInstr &MI, const MachineRegisterInfo &MRI,
const TargetRegisterInfo &TRI) const;
+ /// Returns true if the source registers of \p MI must all be FPRs.
+ bool onlyUsesFP(const MachineInstr &MI, const MachineRegisterInfo &MRI,
+ const TargetRegisterInfo &TRI) const;
+
+ /// Returns true if the destination register of \p MI must be a FPR.
+ bool onlyDefinesFP(const MachineInstr &MI, const MachineRegisterInfo &MRI,
+ const TargetRegisterInfo &TRI) const;
+
public:
AArch64RegisterBankInfo(const TargetRegisterInfo &TRI);
--- /dev/null
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -O0 -mtriple arm64-- -run-pass=regbankselect %s -o - | FileCheck %s
+
+# Check that we correctly assign register banks based off of instructions which
+# only use or only define FPRs.
+#
+# For example, G_SITOFP takes in a GPR, but only ever produces values on FPRs.
+# Some instructions can have inputs/outputs on either FPRs or GPRs. If one of
+# those instructions takes in the result of a G_SITOFP as a source, we should
+# put that source on a FPR.
+#
+# Similarly, G_FPTOSI can only take in a value on a FPR. So, if the result of
+# an instruction is consumed by a G_FPTOSI, we should put the instruction on
+# FPRs.
+
+---
+name: load_only_uses_fp
+legalized: true
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $x0
+ ; CHECK-LABEL: name: load_only_uses_fp
+ ; CHECK: liveins: $x0
+ ; CHECK: [[COPY:%[0-9]+]]:gpr(p0) = COPY $x0
+ ; CHECK: [[C:%[0-9]+]]:fpr(s32) = G_FCONSTANT float 2.000000e+00
+ ; CHECK: [[LOAD:%[0-9]+]]:fpr(s32) = G_LOAD [[COPY]](p0) :: (load 4)
+ ; CHECK: [[FCMP:%[0-9]+]]:gpr(s32) = G_FCMP floatpred(uno), [[C]](s32), [[LOAD]]
+ ; CHECK: $w0 = COPY [[FCMP]](s32)
+ ; CHECK: RET_ReallyLR implicit $w0
+ %0:_(p0) = COPY $x0
+ %1:_(s32) = G_FCONSTANT float 2.0
+ %2:_(s32) = G_LOAD %0 :: (load 4)
+ %3:_(s32) = G_FCMP floatpred(uno), %1, %2
+ $w0 = COPY %3(s32)
+ RET_ReallyLR implicit $w0
+...
+---
+name: unmerge_only_uses_fp
+
+legalized: true
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $x0
+ ; CHECK-LABEL: name: unmerge_only_uses_fp
+ ; CHECK: liveins: $x0
+ ; CHECK: [[COPY:%[0-9]+]]:gpr(s64) = COPY $x0
+ ; CHECK: [[COPY1:%[0-9]+]]:fpr(s64) = COPY [[COPY]](s64)
+ ; CHECK: [[UV:%[0-9]+]]:fpr(s32), [[UV1:%[0-9]+]]:fpr(s32) = G_UNMERGE_VALUES [[COPY1]](s64)
+ ; CHECK: [[FCMP:%[0-9]+]]:gpr(s32) = G_FCMP floatpred(uno), [[UV]](s32), [[UV1]]
+ ; CHECK: $w0 = COPY [[FCMP]](s32)
+ ; CHECK: RET_ReallyLR implicit $w0
+ %0:_(s64) = COPY $x0
+ %1:_(s32), %2:_(s32) = G_UNMERGE_VALUES %0(s64)
+ %3:_(s32) = G_FCMP floatpred(uno), %1, %2
+ $w0 = COPY %3(s32)
+ RET_ReallyLR implicit $w0
+
+...
+---
+name: store_defined_by_fp
+legalized: true
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $x0, $w1
+ ; CHECK-LABEL: name: store_defined_by_fp
+ ; CHECK: liveins: $x0, $w1
+ ; CHECK: [[COPY:%[0-9]+]]:gpr(p0) = COPY $x0
+ ; CHECK: [[COPY1:%[0-9]+]]:gpr(s32) = COPY $w1
+ ; CHECK: [[SITOFP:%[0-9]+]]:fpr(s32) = G_SITOFP [[COPY1]](s32)
+ ; CHECK: G_STORE [[SITOFP]](s32), [[COPY]](p0) :: (store 4)
+ %0:_(p0) = COPY $x0
+ %1:_(s32) = COPY $w1
+ %2:_(s32) = G_SITOFP %1
+ G_STORE %2, %0 :: (store 4)
+
+...
+---
+name: select_defined_by_fp_using_fp
+legalized: true
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $w0, $w1, $w2
+ ; CHECK-LABEL: name: select_defined_by_fp_using_fp
+ ; CHECK: liveins: $w0, $w1, $w2
+ ; CHECK: [[COPY:%[0-9]+]]:gpr(s32) = COPY $w0
+ ; CHECK: [[TRUNC:%[0-9]+]]:gpr(s1) = G_TRUNC %2(s32)
+ ; CHECK: [[COPY1:%[0-9]+]]:gpr(s32) = COPY $w1
+ ; CHECK: [[COPY2:%[0-9]+]]:gpr(s32) = COPY $w2
+ ; CHECK: [[SITOFP:%[0-9]+]]:fpr(s32) = G_SITOFP [[COPY1]](s32)
+ ; CHECK: [[COPY3:%[0-9]+]]:fpr(s1) = COPY [[TRUNC]](s1)
+ ; CHECK: [[COPY4:%[0-9]+]]:fpr(s32) = COPY [[COPY2]](s32)
+ ; CHECK: [[SELECT:%[0-9]+]]:fpr(s32) = G_SELECT [[COPY3]](s1), [[COPY4]], [[SITOFP]]
+ ; CHECK: [[FPTOSI:%[0-9]+]]:gpr(s32) = G_FPTOSI [[SELECT]](s32)
+ %0:_(s32) = COPY $w0
+ %1:_(s1) = G_TRUNC %3(s32)
+ %2:_(s32) = COPY $w1
+ %3:_(s32) = COPY $w2
+ %4:_(s32) = G_SITOFP %2
+ %6:_(s32) = G_SELECT %1(s1), %3, %4
+ %8:_(s32) = G_FPTOSI %6
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