[clang] [RISCV] Correct type lowering of struct of fixed-vector array in VLS (PR #147173)
Brandon Wu via cfe-commits
cfe-commits at lists.llvm.org
Mon Jul 7 17:56:33 PDT 2025
https://github.com/4vtomat updated https://github.com/llvm/llvm-project/pull/147173
>From 1934543b7ec215312eebefd152f7c9151c2d0e54 Mon Sep 17 00:00:00 2001
From: Brandon Wu <songwu0813 at gmail.com>
Date: Sat, 5 Jul 2025 21:32:28 -0700
Subject: [PATCH 1/2] [RISCV] Correct type lowering of struct of fixed-vector
array in VLS
Currently, struct of fixed-vector array is flattened and lowered to
scalable vector. However only struct of 1-element-fixed-vector array
should be lowered that way, struct of fixed-vector array of length >1
should be lowered to vector tuple type.
https://github.com/riscv-non-isa/riscv-elf-psabi-doc/pull/418/files#diff-3a934f00cffdb3e509722753126a2cf6082a7648ab3b9ca8cbb0e84f8a6a12edR555-R558
---
clang/lib/CodeGen/Targets/RISCV.cpp | 144 ++++++++----------
.../RISCV/riscv-vector-callingconv-llvm-ir.c | 8 +-
.../riscv-vector-callingconv-llvm-ir.cpp | 8 +-
3 files changed, 68 insertions(+), 92 deletions(-)
diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index cc3d487da83b5..e1603d3095a04 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -441,98 +441,74 @@ bool RISCVABIInfo::detectVLSCCEligibleStruct(QualType Ty, unsigned ABIVLen,
// __attribute__((vector_size(64))) int d;
// }
//
- // Struct of 1 fixed-length vector is passed as a scalable vector.
- // Struct of >1 fixed-length vectors are passed as vector tuple.
- // Struct of 1 array of fixed-length vectors is passed as a scalable vector.
- // Otherwise, pass the struct indirectly.
-
- if (llvm::StructType *STy = dyn_cast<llvm::StructType>(CGT.ConvertType(Ty))) {
- unsigned NumElts = STy->getStructNumElements();
- if (NumElts > 8)
- return false;
+ // 1. Struct of 1 fixed-length vector is passed as a scalable vector.
+ // 2. Struct of >1 fixed-length vectors are passed as vector tuple.
+ // 3. Struct of an array with 1 element of fixed-length vectors is passed as a
+ // scalable vector.
+ // 4. Struct of an array with >1 elements of fixed-length vectors is passed as
+ // vector tuple.
+ // 5. Otherwise, pass the struct indirectly.
+
+ llvm::StructType *STy = dyn_cast<llvm::StructType>(CGT.ConvertType(Ty));
+ if (!STy)
+ return false;
- auto *FirstEltTy = STy->getElementType(0);
- if (!STy->containsHomogeneousTypes())
- return false;
+ unsigned NumElts = STy->getStructNumElements();
+ if (NumElts > 8)
+ return false;
- // Check structure of fixed-length vectors and turn them into vector tuple
- // type if legal.
- if (auto *FixedVecTy = dyn_cast<llvm::FixedVectorType>(FirstEltTy)) {
- if (NumElts == 1) {
- // Handle single fixed-length vector.
- VLSType = llvm::ScalableVectorType::get(
- FixedVecTy->getElementType(),
- llvm::divideCeil(FixedVecTy->getNumElements() *
- llvm::RISCV::RVVBitsPerBlock,
- ABIVLen));
- // Check registers needed <= 8.
- return llvm::divideCeil(
- FixedVecTy->getNumElements() *
- FixedVecTy->getElementType()->getScalarSizeInBits(),
- ABIVLen) <= 8;
- }
- // LMUL
- // = fixed-length vector size / ABIVLen
- // = 8 * I8EltCount / RVVBitsPerBlock
- // =>
- // I8EltCount
- // = (fixed-length vector size * RVVBitsPerBlock) / (ABIVLen * 8)
- unsigned I8EltCount = llvm::divideCeil(
- FixedVecTy->getNumElements() *
- FixedVecTy->getElementType()->getScalarSizeInBits() *
- llvm::RISCV::RVVBitsPerBlock,
- ABIVLen * 8);
- VLSType = llvm::TargetExtType::get(
- getVMContext(), "riscv.vector.tuple",
- llvm::ScalableVectorType::get(llvm::Type::getInt8Ty(getVMContext()),
- I8EltCount),
- NumElts);
- // Check registers needed <= 8.
- return NumElts *
- llvm::divideCeil(
- FixedVecTy->getNumElements() *
- FixedVecTy->getElementType()->getScalarSizeInBits(),
- ABIVLen) <=
- 8;
- }
+ auto *FirstEltTy = STy->getElementType(0);
+ if (!STy->containsHomogeneousTypes())
+ return false;
- // If elements are not fixed-length vectors, it should be an array.
+ if (auto *ArrayTy = dyn_cast<llvm::ArrayType>(FirstEltTy)) {
+ // Only struct of single array is accepted
if (NumElts != 1)
return false;
+ FirstEltTy = ArrayTy->getArrayElementType();
+ NumElts = ArrayTy->getNumElements();
+ }
- // Check array of fixed-length vector and turn it into scalable vector type
- // if legal.
- if (auto *ArrTy = dyn_cast<llvm::ArrayType>(FirstEltTy)) {
- unsigned NumArrElt = ArrTy->getNumElements();
- if (NumArrElt > 8)
- return false;
-
- auto *ArrEltTy = dyn_cast<llvm::FixedVectorType>(ArrTy->getElementType());
- if (!ArrEltTy)
- return false;
+ auto *FixedVecTy = dyn_cast<llvm::FixedVectorType>(FirstEltTy);
+ if (!FixedVecTy)
+ return false;
- // LMUL
- // = NumArrElt * fixed-length vector size / ABIVLen
- // = fixed-length vector elt size * ScalVecNumElts / RVVBitsPerBlock
- // =>
- // ScalVecNumElts
- // = (NumArrElt * fixed-length vector size * RVVBitsPerBlock) /
- // (ABIVLen * fixed-length vector elt size)
- // = NumArrElt * num fixed-length vector elt * RVVBitsPerBlock /
- // ABIVLen
- unsigned ScalVecNumElts = llvm::divideCeil(
- NumArrElt * ArrEltTy->getNumElements() * llvm::RISCV::RVVBitsPerBlock,
- ABIVLen);
- VLSType = llvm::ScalableVectorType::get(ArrEltTy->getElementType(),
- ScalVecNumElts);
- // Check registers needed <= 8.
- return llvm::divideCeil(
- ScalVecNumElts *
- ArrEltTy->getElementType()->getScalarSizeInBits(),
- llvm::RISCV::RVVBitsPerBlock) <= 8;
- }
+ // Turn them into scalable vector type or vector tuple type if legal.
+ if (NumElts == 1) {
+ // Handle single fixed-length vector.
+ VLSType = llvm::ScalableVectorType::get(
+ FixedVecTy->getElementType(),
+ llvm::divideCeil(FixedVecTy->getNumElements() *
+ llvm::RISCV::RVVBitsPerBlock,
+ ABIVLen));
+ // Check registers needed <= 8.
+ return llvm::divideCeil(
+ FixedVecTy->getNumElements() *
+ FixedVecTy->getElementType()->getScalarSizeInBits(),
+ ABIVLen) <= 8;
}
- return false;
+ // LMUL
+ // = fixed-length vector size / ABIVLen
+ // = 8 * I8EltCount / RVVBitsPerBlock
+ // =>
+ // I8EltCount
+ // = (fixed-length vector size * RVVBitsPerBlock) / (ABIVLen * 8)
+ unsigned I8EltCount =
+ llvm::divideCeil(FixedVecTy->getNumElements() *
+ FixedVecTy->getElementType()->getScalarSizeInBits() *
+ llvm::RISCV::RVVBitsPerBlock,
+ ABIVLen * 8);
+ VLSType = llvm::TargetExtType::get(
+ getVMContext(), "riscv.vector.tuple",
+ llvm::ScalableVectorType::get(llvm::Type::getInt8Ty(getVMContext()),
+ I8EltCount),
+ NumElts);
+ // Check registers needed <= 8.
+ return NumElts * llvm::divideCeil(
+ FixedVecTy->getNumElements() *
+ FixedVecTy->getElementType()->getScalarSizeInBits(),
+ ABIVLen) <=
+ 8;
}
// Fixed-length RVV vectors are represented as scalable vectors in function
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
index 3044d91f1c31c..82e43fff0c3aa 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.c
@@ -153,14 +153,14 @@ void __attribute__((riscv_vls_cc)) test_st_i32x4_arr1(struct st_i32x4_arr1 arg)
// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @test_st_i32x4_arr1_256(<vscale x 1 x i32> %arg)
void __attribute__((riscv_vls_cc(256))) test_st_i32x4_arr1_256(struct st_i32x4_arr1 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @test_st_i32x4_arr4(<vscale x 8 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @test_st_i32x4_arr4(target("riscv.vector.tuple", <vscale x 8 x i8>, 4) %arg)
void __attribute__((riscv_vls_cc)) test_st_i32x4_arr4(struct st_i32x4_arr4 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @test_st_i32x4_arr4_256(<vscale x 4 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @test_st_i32x4_arr4_256(target("riscv.vector.tuple", <vscale x 4 x i8>, 4) %arg)
void __attribute__((riscv_vls_cc(256))) test_st_i32x4_arr4_256(struct st_i32x4_arr4 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @test_st_i32x4_arr8(<vscale x 16 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @test_st_i32x4_arr8(target("riscv.vector.tuple", <vscale x 8 x i8>, 8) %arg)
void __attribute__((riscv_vls_cc)) test_st_i32x4_arr8(struct st_i32x4_arr8 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @test_st_i32x4_arr8_256(<vscale x 8 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @test_st_i32x4_arr8_256(target("riscv.vector.tuple", <vscale x 4 x i8>, 8) %arg)
void __attribute__((riscv_vls_cc(256))) test_st_i32x4_arr8_256(struct st_i32x4_arr8 arg) {}
// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @test_st_i32x4x2(target("riscv.vector.tuple", <vscale x 8 x i8>, 2) %arg)
diff --git a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
index 594bfe159b28c..5f6539796c20d 100644
--- a/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
+++ b/clang/test/CodeGen/RISCV/riscv-vector-callingconv-llvm-ir.cpp
@@ -133,14 +133,14 @@ typedef int __attribute__((vector_size(256))) int32x64_t;
// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @_Z22test_st_i32x4_arr1_25613st_i32x4_arr1(<vscale x 1 x i32> %arg)
[[riscv::vls_cc(256)]] void test_st_i32x4_arr1_256(struct st_i32x4_arr1 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @_Z18test_st_i32x4_arr413st_i32x4_arr4(<vscale x 8 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @_Z18test_st_i32x4_arr413st_i32x4_arr4(target("riscv.vector.tuple", <vscale x 8 x i8>, 4) %arg)
[[riscv::vls_cc]] void test_st_i32x4_arr4(struct st_i32x4_arr4 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @_Z22test_st_i32x4_arr4_25613st_i32x4_arr4(<vscale x 4 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @_Z22test_st_i32x4_arr4_25613st_i32x4_arr4(target("riscv.vector.tuple", <vscale x 4 x i8>, 4) %arg)
[[riscv::vls_cc(256)]] void test_st_i32x4_arr4_256(struct st_i32x4_arr4 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @_Z18test_st_i32x4_arr813st_i32x4_arr8(<vscale x 16 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @_Z18test_st_i32x4_arr813st_i32x4_arr8(target("riscv.vector.tuple", <vscale x 8 x i8>, 8) %arg)
[[riscv::vls_cc]] void test_st_i32x4_arr8(struct st_i32x4_arr8 arg) {}
-// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @_Z22test_st_i32x4_arr8_25613st_i32x4_arr8(<vscale x 8 x i32> %arg)
+// CHECK-LLVM: define dso_local riscv_vls_cc(256) void @_Z22test_st_i32x4_arr8_25613st_i32x4_arr8(target("riscv.vector.tuple", <vscale x 4 x i8>, 8) %arg)
[[riscv::vls_cc(256)]] void test_st_i32x4_arr8_256(struct st_i32x4_arr8 arg) {}
// CHECK-LLVM: define dso_local riscv_vls_cc(128) void @_Z15test_st_i32x4x210st_i32x4x2(target("riscv.vector.tuple", <vscale x 8 x i8>, 2) %arg)
>From 4bf03a015fdd37cd9323ece6697dc79196df3446 Mon Sep 17 00:00:00 2001
From: Brandon Wu <songwu0813 at gmail.com>
Date: Mon, 7 Jul 2025 17:56:04 -0700
Subject: [PATCH 2/2] fixup! [RISCV] Correct type lowering of struct of
fixed-vector array in VLS
---
clang/lib/CodeGen/Targets/RISCV.cpp | 22 +++++++++++-----------
1 file changed, 11 insertions(+), 11 deletions(-)
diff --git a/clang/lib/CodeGen/Targets/RISCV.cpp b/clang/lib/CodeGen/Targets/RISCV.cpp
index e1603d3095a04..e3232b61a693c 100644
--- a/clang/lib/CodeGen/Targets/RISCV.cpp
+++ b/clang/lib/CodeGen/Targets/RISCV.cpp
@@ -473,6 +473,14 @@ bool RISCVABIInfo::detectVLSCCEligibleStruct(QualType Ty, unsigned ABIVLen,
if (!FixedVecTy)
return false;
+ // Check registers needed <= 8.
+ if (NumElts * llvm::divideCeil(
+ FixedVecTy->getNumElements() *
+ FixedVecTy->getElementType()->getScalarSizeInBits(),
+ ABIVLen) >
+ 8)
+ return false;
+
// Turn them into scalable vector type or vector tuple type if legal.
if (NumElts == 1) {
// Handle single fixed-length vector.
@@ -481,12 +489,9 @@ bool RISCVABIInfo::detectVLSCCEligibleStruct(QualType Ty, unsigned ABIVLen,
llvm::divideCeil(FixedVecTy->getNumElements() *
llvm::RISCV::RVVBitsPerBlock,
ABIVLen));
- // Check registers needed <= 8.
- return llvm::divideCeil(
- FixedVecTy->getNumElements() *
- FixedVecTy->getElementType()->getScalarSizeInBits(),
- ABIVLen) <= 8;
+ return true;
}
+
// LMUL
// = fixed-length vector size / ABIVLen
// = 8 * I8EltCount / RVVBitsPerBlock
@@ -503,12 +508,7 @@ bool RISCVABIInfo::detectVLSCCEligibleStruct(QualType Ty, unsigned ABIVLen,
llvm::ScalableVectorType::get(llvm::Type::getInt8Ty(getVMContext()),
I8EltCount),
NumElts);
- // Check registers needed <= 8.
- return NumElts * llvm::divideCeil(
- FixedVecTy->getNumElements() *
- FixedVecTy->getElementType()->getScalarSizeInBits(),
- ABIVLen) <=
- 8;
+ return true;
}
// Fixed-length RVV vectors are represented as scalable vectors in function
More information about the cfe-commits
mailing list