[HLSL][Sema] Fix Struct Size Calculation containing 16/32 bit scalars #128086
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
llvmbot
added
clang
Member
|
@llvm/pr-subscribers-hlsl Author: Ashley Coleman (V-FEXrt) ChangesFixes #119641 Update SemaHLSL to correctly calculate the alignment barrier for scalars that are not 4 bytes wide Full diff: https://github.com/llvm/llvm-project/pull/128086.diff 2 Files Affected:
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index d26d85d5861b1..cccfd4aec7eb2 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -172,6 +172,27 @@ Decl *SemaHLSL::ActOnStartBuffer(Scope *BufferScope, bool CBuffer,
return Result;
}
+static unsigned calculateLegacyCbufferFieldAlign(const ASTContext &Context,
+ QualType T) {
+ // Aggregate types are always aligned to new buffer rows
+ if (T->isAggregateType())
+ return 16;
+
+ assert(Context.getTypeSize(T) <= 64 &&
+ "Scalar bit widths larger than 64 not supported");
+
+ // 64 bit types such as double and uint64_t align to 8 bytes
+ if (Context.getTypeSize(T) == 64)
+ return 8;
+
+ // Half types align to 2 bytes only if native half is available
+ if (T->isHalfType() && Context.getLangOpts().NativeHalfType)
+ return 2;
+
+ // Everything else aligns to 4 bytes
+ return 4;
+}
+
// Calculate the size of a legacy cbuffer type in bytes based on
// https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-packing-rules
static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
@@ -183,11 +204,7 @@ static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
for (const FieldDecl *Field : RD->fields()) {
QualType Ty = Field->getType();
unsigned FieldSize = calculateLegacyCbufferSize(Context, Ty);
- // FIXME: This is not the correct alignment, it does not work for 16-bit
- // types. See llvm/llvm-project#119641.
- unsigned FieldAlign = 4;
- if (Ty->isAggregateType())
- FieldAlign = CBufferAlign;
+ unsigned FieldAlign = calculateLegacyCbufferFieldAlign(Context, Ty);
Size = llvm::alignTo(Size, FieldAlign);
Size += FieldSize;
}
diff --git a/clang/test/CodeGenHLSL/cbuffer_align.hlsl b/clang/test/CodeGenHLSL/cbuffer_align.hlsl
new file mode 100644
index 0000000000000..31db2e0726020
--- /dev/null
+++ b/clang/test/CodeGenHLSL/cbuffer_align.hlsl
@@ -0,0 +1,60 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: dxil-pc-shadermodel6.3-library %s -fnative-half-type \
+// RUN: -emit-llvm -disable-llvm-passes -o - | FileCheck %s --check-prefix=CHECK-HALF
+
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: dxil-pc-shadermodel6.3-library %s \
+// RUN: -emit-llvm -disable-llvm-passes -o - | FileCheck %s --check-prefix=CHECK-FLOAT
+
+
+struct S1 {
+ half a; // 2 bytes + 2 bytes pad or 4 bytes
+ float b; // 4 bytes
+ half c; // 2 bytes + 2 bytes pad or 4 bytes
+ float d; // 4 bytes
+ double e; // 8 bytes
+};
+
+struct S2 {
+ half a; // 2 bytes or 4 bytes
+ half b; // 2 bytes or 4 bytes
+ float e; // 4 bytes or 4 bytes + 4 padding
+ double f; // 8 bytes
+};
+
+struct S3 {
+ half a; // 2 bytes + 6 bytes pad or 4 bytes + 4 bytes pad
+ uint64_t b; // 8 bytes
+};
+
+struct S4 {
+ float a; // 4 bytes
+ half b; // 2 bytes or 4 bytes
+ half c; // 2 bytes or 4 bytes + 4 bytes pad
+ double d; // 8 bytes
+};
+
+
+cbuffer CB0 {
+ // CHECK-HALF: @CB0.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB0, 24, 0))
+ // CHECK-FLOAT: @CB0.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB0, 24, 0))
+ S1 s1;
+}
+
+cbuffer CB1 {
+ // CHECK-HALF: @CB1.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB1, 16, 0))
+ // CHECK-FLOAT: @CB1.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB1, 24, 0))
+ S2 s2;
+}
+
+cbuffer CB2 {
+ // CHECK-HALF: @CB2.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB2, 16, 0))
+ // CHECK-FLOAT: @CB2.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB2, 16, 0))
+ S3 s3;
+}
+
+cbuffer CB3 {
+ // CHECK-HALF: @CB3.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB3, 16, 0))
+ // CHECK-FLOAT: @CB3.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB3, 24, 0))
+ S4 s4;
+}
|
Member
|
@llvm/pr-subscribers-clang Author: Ashley Coleman (V-FEXrt) ChangesFixes #119641 Update SemaHLSL to correctly calculate the alignment barrier for scalars that are not 4 bytes wide Full diff: https://github.com/llvm/llvm-project/pull/128086.diff 2 Files Affected:
diff --git a/clang/lib/Sema/SemaHLSL.cpp b/clang/lib/Sema/SemaHLSL.cpp
index d26d85d5861b1..cccfd4aec7eb2 100644
--- a/clang/lib/Sema/SemaHLSL.cpp
+++ b/clang/lib/Sema/SemaHLSL.cpp
@@ -172,6 +172,27 @@ Decl *SemaHLSL::ActOnStartBuffer(Scope *BufferScope, bool CBuffer,
return Result;
}
+static unsigned calculateLegacyCbufferFieldAlign(const ASTContext &Context,
+ QualType T) {
+ // Aggregate types are always aligned to new buffer rows
+ if (T->isAggregateType())
+ return 16;
+
+ assert(Context.getTypeSize(T) <= 64 &&
+ "Scalar bit widths larger than 64 not supported");
+
+ // 64 bit types such as double and uint64_t align to 8 bytes
+ if (Context.getTypeSize(T) == 64)
+ return 8;
+
+ // Half types align to 2 bytes only if native half is available
+ if (T->isHalfType() && Context.getLangOpts().NativeHalfType)
+ return 2;
+
+ // Everything else aligns to 4 bytes
+ return 4;
+}
+
// Calculate the size of a legacy cbuffer type in bytes based on
// https://learn.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-packing-rules
static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
@@ -183,11 +204,7 @@ static unsigned calculateLegacyCbufferSize(const ASTContext &Context,
for (const FieldDecl *Field : RD->fields()) {
QualType Ty = Field->getType();
unsigned FieldSize = calculateLegacyCbufferSize(Context, Ty);
- // FIXME: This is not the correct alignment, it does not work for 16-bit
- // types. See llvm/llvm-project#119641.
- unsigned FieldAlign = 4;
- if (Ty->isAggregateType())
- FieldAlign = CBufferAlign;
+ unsigned FieldAlign = calculateLegacyCbufferFieldAlign(Context, Ty);
Size = llvm::alignTo(Size, FieldAlign);
Size += FieldSize;
}
diff --git a/clang/test/CodeGenHLSL/cbuffer_align.hlsl b/clang/test/CodeGenHLSL/cbuffer_align.hlsl
new file mode 100644
index 0000000000000..31db2e0726020
--- /dev/null
+++ b/clang/test/CodeGenHLSL/cbuffer_align.hlsl
@@ -0,0 +1,60 @@
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: dxil-pc-shadermodel6.3-library %s -fnative-half-type \
+// RUN: -emit-llvm -disable-llvm-passes -o - | FileCheck %s --check-prefix=CHECK-HALF
+
+// RUN: %clang_cc1 -std=hlsl2021 -finclude-default-header -x hlsl -triple \
+// RUN: dxil-pc-shadermodel6.3-library %s \
+// RUN: -emit-llvm -disable-llvm-passes -o - | FileCheck %s --check-prefix=CHECK-FLOAT
+
+
+struct S1 {
+ half a; // 2 bytes + 2 bytes pad or 4 bytes
+ float b; // 4 bytes
+ half c; // 2 bytes + 2 bytes pad or 4 bytes
+ float d; // 4 bytes
+ double e; // 8 bytes
+};
+
+struct S2 {
+ half a; // 2 bytes or 4 bytes
+ half b; // 2 bytes or 4 bytes
+ float e; // 4 bytes or 4 bytes + 4 padding
+ double f; // 8 bytes
+};
+
+struct S3 {
+ half a; // 2 bytes + 6 bytes pad or 4 bytes + 4 bytes pad
+ uint64_t b; // 8 bytes
+};
+
+struct S4 {
+ float a; // 4 bytes
+ half b; // 2 bytes or 4 bytes
+ half c; // 2 bytes or 4 bytes + 4 bytes pad
+ double d; // 8 bytes
+};
+
+
+cbuffer CB0 {
+ // CHECK-HALF: @CB0.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB0, 24, 0))
+ // CHECK-FLOAT: @CB0.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB0, 24, 0))
+ S1 s1;
+}
+
+cbuffer CB1 {
+ // CHECK-HALF: @CB1.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB1, 16, 0))
+ // CHECK-FLOAT: @CB1.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB1, 24, 0))
+ S2 s2;
+}
+
+cbuffer CB2 {
+ // CHECK-HALF: @CB2.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB2, 16, 0))
+ // CHECK-FLOAT: @CB2.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB2, 16, 0))
+ S3 s3;
+}
+
+cbuffer CB3 {
+ // CHECK-HALF: @CB3.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB3, 16, 0))
+ // CHECK-FLOAT: @CB3.cb = external constant target("dx.CBuffer", target("dx.Layout", %__cblayout_CB3, 24, 0))
+ S4 s4;
+}
|
tex3d
reviewed
Feb 20, 2025
Contributor
tex3d
left a comment
tex3d
left a comment
There was a problem hiding this comment.
What happens for vector fields?
hekota
reviewed
Feb 21, 2025
Contributor
Author
tex3d
reviewed
Feb 25, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Fixes #119641
Update SemaHLSL to correctly calculate the alignment barrier for scalars that are not 4 bytes wide