[llvm] [RISCV][GISEL] Legalize G_VAARG through expansion. (PR #73065)
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Tue Nov 21 17:41:59 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-backend-risc-v
Author: Michael Maitland (michaelmaitland)
<details>
<summary>Changes</summary>
G_VAARG can be expanded similiar to SelectionDAG::expandVAArg through LegalizerHelper::lower. This patch implements the lowering through this style of expansion.
The expansion gets the head of the va_list by loading the pointer to va_list. Then, the head of the list is adjusted depending on argument alignment information. This gives a pointer to the element to be read out of the va_list. Next, the head of the va_list is bumped to the next element in the list. The new head of the list is stored back to the original pointer to the head of the va_list so that subsequent G_VAARG instructions get the next element in the list. Lastly, the element is loaded from the alignment adjusted pointer constructed earlier.
---
Full diff: https://github.com/llvm/llvm-project/pull/73065.diff
5 Files Affected:
- (modified) llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h (+1)
- (modified) llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp (+67)
- (modified) llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp (+5)
- (added) llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-vaarg.mir (+40)
- (added) llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv64/legalize-vaarg.mir (+40)
``````````diff
diff --git a/llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h b/llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
index 86d3cb2bedb95b6..350c91ad6fa4f61 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/LegalizerHelper.h
@@ -430,6 +430,7 @@ class LegalizerHelper {
LegalizeResult lowerVectorReduction(MachineInstr &MI);
LegalizeResult lowerMemcpyInline(MachineInstr &MI);
LegalizeResult lowerMemCpyFamily(MachineInstr &MI, unsigned MaxLen = 0);
+ LegalizeResult lowerVAArg(MachineInstr &MI);
};
/// Helper function that creates a libcall to the given \p Name using the given
diff --git a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
index dd5577d47f97764..310b71dca37bf3c 100644
--- a/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/LegalizerHelper.cpp
@@ -3780,6 +3780,8 @@ LegalizerHelper::lower(MachineInstr &MI, unsigned TypeIdx, LLT LowerHintTy) {
return lowerTRUNC(MI);
GISEL_VECREDUCE_CASES_NONSEQ
return lowerVectorReduction(MI);
+ case G_VAARG:
+ return lowerVAArg(MI);
}
}
@@ -7865,6 +7867,71 @@ LegalizerHelper::lowerVectorReduction(MachineInstr &MI) {
return UnableToLegalize;
}
+static Type *getTypeForLLT(LLT Ty, LLVMContext &C);
+
+LegalizerHelper::LegalizeResult LegalizerHelper::lowerVAArg(MachineInstr &MI) {
+ Observer.changingInstr(MI);
+ MachineFunction &MF = *MI.getMF();
+ const DataLayout &DL = MIRBuilder.getDataLayout();
+ LLVMContext &Ctx = MF.getFunction().getContext();
+ Register ListPtr = MI.getOperand(1).getReg();
+ LLT PtrTy = MRI.getType(ListPtr);
+
+ // LstPtr is a pointer to the head of the list. Get the address
+ // of the head of the list.
+ Align PtrAlignment = Align(DL.getABITypeAlign(getTypeForLLT(PtrTy, Ctx)));
+ MachineMemOperand *PtrLoadMMO =
+ MF.getMachineMemOperand(MachinePointerInfo::getUnknownStack(MF),
+ MachineMemOperand::MOLoad, PtrTy, PtrAlignment);
+ Register HeadOfList = MRI.createGenericVirtualRegister(PtrTy);
+ Register VAList =
+ MIRBuilder.buildLoad(HeadOfList, ListPtr, *PtrLoadMMO).getReg(0);
+
+ const MaybeAlign MA(MI.getOperand(2).getImm());
+ LLT PtrTyAsScalarTy = LLT::scalar(PtrTy.getSizeInBits());
+ if (MA && *MA > TLI.getMinStackArgumentAlignment()) {
+ Register AlignAmt =
+ MIRBuilder.buildConstant(PtrTyAsScalarTy, MA->value() - 1).getReg(0);
+ Register AddDst = MRI.createGenericVirtualRegister(PtrTy);
+ MIRBuilder.buildPtrAdd(AddDst, HeadOfList, AlignAmt);
+ Register Mask =
+ MIRBuilder.buildConstant(PtrTyAsScalarTy, -(int64_t)MA->value())
+ .getReg(0);
+ Register AndDst = MRI.createGenericVirtualRegister(PtrTy);
+ VAList = MIRBuilder.buildPtrMask(AndDst, AddDst, Mask).getReg(0);
+ }
+
+ // Increment the pointer, VAList, to the next vaarg
+ // The list should be bumped by the size of element in the current head of
+ // list.
+ Register Dst = MI.getOperand(0).getReg();
+ LLT Ty = MRI.getType(Dst);
+ Register IncAmt =
+ MIRBuilder
+ .buildConstant(PtrTyAsScalarTy,
+ DL.getTypeAllocSize(getTypeForLLT(Ty, Ctx)))
+ .getReg(0);
+ Register Succ = MRI.createGenericVirtualRegister(PtrTy);
+ MIRBuilder.buildPtrAdd(Succ, VAList, IncAmt);
+
+ // Store the increment VAList to the legalized pointer
+ MachineMemOperand *StoreMMO =
+ MF.getMachineMemOperand(MachinePointerInfo::getUnknownStack(MF),
+ MachineMemOperand::MOStore, PtrTy, PtrAlignment);
+ MIRBuilder.buildStore(Succ, ListPtr, *StoreMMO);
+ // Load the actual argument out of the pointer VAList
+ Align EltAlignment = Align(DL.getABITypeAlign(getTypeForLLT(Ty, Ctx)));
+ MachineMemOperand *EltLoadMMO =
+ MF.getMachineMemOperand(MachinePointerInfo::getUnknownStack(MF),
+ MachineMemOperand::MOLoad, Ty, EltAlignment);
+ MIRBuilder.buildLoad(Dst, VAList, *EltLoadMMO);
+
+ Observer.changedInstr(MI);
+ Observer.erasingInstr(MI);
+ MI.eraseFromParent();
+ return Legalized;
+}
+
static bool shouldLowerMemFuncForSize(const MachineFunction &MF) {
// On Darwin, -Os means optimize for size without hurting performance, so
// only really optimize for size when -Oz (MinSize) is used.
diff --git a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
index 9eb5812e024b915..f9e753daff1fbf5 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVLegalizerInfo.cpp
@@ -261,6 +261,11 @@ RISCVLegalizerInfo::RISCVLegalizerInfo(const RISCVSubtarget &ST) {
getActionDefinitionsBuilder({G_FCEIL, G_FFLOOR})
.libcallFor({s32, s64});
+ // va_list must be a pointer, but most sized types are pretty easy to handle
+ // as the destination.
+ getActionDefinitionsBuilder(G_VAARG).lowerForCartesianProduct(
+ {s8, s16, s32, s64, p0}, {p0});
+
getLegacyLegalizerInfo().computeTables();
}
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-vaarg.mir b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-vaarg.mir
new file mode 100644
index 000000000000000..4876e0d5ee96b2f
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv32/legalize-vaarg.mir
@@ -0,0 +1,40 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv32 -run-pass=legalizer %s -o - | FileCheck %s
+
+# On RISC-V, the MinStackArgumentAlignment is 1 and the ABI Alignment for p0 is
+# greater than 1, so we will always generate code to adjust for this alignment.
+
+--- |
+ define void @va_arg() {
+ %va = alloca ptr, align 4
+ %1 = va_arg ptr %va, i32
+ ret void
+ }
+...
+---
+name: va_arg
+legalized: false
+tracksRegLiveness: true
+stack:
+ - { id: 0, name: va, type: default, offset: 0, size: 4, alignment: 4,
+ stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+ debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body: |
+ bb.1 (%ir-block.0):
+ ; CHECK-LABEL: name: va_arg
+ ; CHECK: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0.va
+ ; CHECK-NEXT: [[LOAD:%[0-9]+]]:_(p0) = G_LOAD [[FRAME_INDEX]](p0) :: (load (p0))
+ ; CHECK-NEXT: [[C:%[0-9]+]]:_(s32) = G_CONSTANT i32 3
+ ; CHECK-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[LOAD]], [[C]](s32)
+ ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s32) = G_CONSTANT i32 -4
+ ; CHECK-NEXT: [[PTRTOINT:%[0-9]+]]:_(s32) = G_PTRTOINT [[PTR_ADD]](p0)
+ ; CHECK-NEXT: [[AND:%[0-9]+]]:_(s32) = G_AND [[PTRTOINT]], [[C1]]
+ ; CHECK-NEXT: [[INTTOPTR:%[0-9]+]]:_(p0) = G_INTTOPTR [[AND]](s32)
+ ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s32) = G_CONSTANT i32 4
+ ; CHECK-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[INTTOPTR]], [[C2]](s32)
+ ; CHECK-NEXT: G_STORE [[PTR_ADD1]](p0), [[FRAME_INDEX]](p0) :: (store (p0))
+ ; CHECK-NEXT: PseudoRET
+ %0:_(p0) = G_FRAME_INDEX %stack.0.va
+ %1:_(s32) = G_VAARG %0(p0), 4
+ PseudoRET
+...
diff --git a/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv64/legalize-vaarg.mir b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv64/legalize-vaarg.mir
new file mode 100644
index 000000000000000..c32f590479c7aa3
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/GlobalISel/legalizer/rv64/legalize-vaarg.mir
@@ -0,0 +1,40 @@
+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py
+# RUN: llc -mtriple=riscv64 -run-pass=legalizer %s -o - | FileCheck %s
+
+# On RISC-V, the MinStackArgumentAlignment is 1 and the ABI Alignment for p0 is
+# greater than 1, so we will always generate code to adjust for this alignment.
+
+--- |
+ define void @va_arg() {
+ %va = alloca ptr, align 8
+ %1 = va_arg ptr %va, i32
+ ret void
+ }
+...
+---
+name: va_arg
+legalized: false
+tracksRegLiveness: true
+stack:
+ - { id: 0, name: va, type: default, offset: 0, size: 8, alignment: 4,
+ stack-id: default, callee-saved-register: '', callee-saved-restored: true,
+ debug-info-variable: '', debug-info-expression: '', debug-info-location: '' }
+body: |
+ bb.1 (%ir-block.0):
+ ; CHECK-LABEL: name: va_arg
+ ; CHECK: [[FRAME_INDEX:%[0-9]+]]:_(p0) = G_FRAME_INDEX %stack.0.va
+ ; CHECK-NEXT: [[LOAD:%[0-9]+]]:_(p0) = G_LOAD [[FRAME_INDEX]](p0) :: (load (p0))
+ ; CHECK-NEXT: [[C:%[0-9]+]]:_(s64) = G_CONSTANT i64 3
+ ; CHECK-NEXT: [[PTR_ADD:%[0-9]+]]:_(p0) = G_PTR_ADD [[LOAD]], [[C]](s64)
+ ; CHECK-NEXT: [[C1:%[0-9]+]]:_(s64) = G_CONSTANT i64 -4
+ ; CHECK-NEXT: [[PTRTOINT:%[0-9]+]]:_(s64) = G_PTRTOINT [[PTR_ADD]](p0)
+ ; CHECK-NEXT: [[AND:%[0-9]+]]:_(s64) = G_AND [[PTRTOINT]], [[C1]]
+ ; CHECK-NEXT: [[INTTOPTR:%[0-9]+]]:_(p0) = G_INTTOPTR [[AND]](s64)
+ ; CHECK-NEXT: [[C2:%[0-9]+]]:_(s64) = G_CONSTANT i64 4
+ ; CHECK-NEXT: [[PTR_ADD1:%[0-9]+]]:_(p0) = G_PTR_ADD [[INTTOPTR]], [[C2]](s64)
+ ; CHECK-NEXT: G_STORE [[PTR_ADD1]](p0), [[FRAME_INDEX]](p0) :: (store (p0))
+ ; CHECK-NEXT: PseudoRET
+ %0:_(p0) = G_FRAME_INDEX %stack.0.va
+ %1:_(s32) = G_VAARG %0(p0), 4
+ PseudoRET
+...
``````````
</details>
https://github.com/llvm/llvm-project/pull/73065
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