[clang] [clang] Support constexpr alignment of __builtin_assume_aligned. (PR #127223)

[Tang Jiajun via cfe-commits]

https://github.com/tangjj11 updated https://github.com/llvm/llvm-project/pull/127223

>From 5c83ee47a5927645ded9ec0af061ff21c094f008 Mon Sep 17 00:00:00 2001
From: Tang Jiajun <1220586548 at qq.com>
Date: Sat, 15 Feb 2025 00:35:34 +0800
Subject: [PATCH 1/3] Add test.

---
 clang/test/CodeGen/builtin-assume-aligned.cpp | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
 create mode 100644 clang/test/CodeGen/builtin-assume-aligned.cpp

diff --git a/clang/test/CodeGen/builtin-assume-aligned.cpp b/clang/test/CodeGen/builtin-assume-aligned.cpp
new file mode 100644
index 0000000000000..fae4221d7d7e7
--- /dev/null
+++ b/clang/test/CodeGen/builtin-assume-aligned.cpp
@@ -0,0 +1,17 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py
+// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
+
+constexpr int get_align() { return 1; }
+
+// CHECK-LABEL: @Ztest1P(
+// CHECK-NEXT:  entry:
+// CHECK-NEXT:    [[A_ADDR:%.*]] = alloca ptr, align 8
+// CHECK-NEXT:    store ptr [[A:%.*]], ptr [[A_ADDR]], align 8
+// CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[A_ADDR]], align 8
+// CHECK-NEXT:    call void @llvm.assume(i1 true) [ "align"(ptr [[TMP0]], i64 32, i64 0) ]
+// CHECK-NEXT:    store ptr [[TMP0]], ptr [[A_ADDR]], align 8
+// CHECK-NEXT:    [[TMP3:%.*]] = load ptr, ptr [[A_ADDR]], align 8
+// CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[TMP3]], i64 0
+// CHECK-NEXT:    [[TMP4:%.*]] = load i32, ptr [[ARRAYIDX]], align 4
+// CHECK-NEXT:    ret i32 [[TMP4]]
+void *test1(void *a) { return __builtin_assume_aligned(a, 32, get_align()); }

>From ada1d827164472676fc3cc36fb8b0bca5e053286 Mon Sep 17 00:00:00 2001
From: Tang Jiajun <1220586548 at qq.com>
Date: Sat, 15 Feb 2025 00:37:25 +0800
Subject: [PATCH 2/3] support constexpr alignment of __builtin_assume_aligned.

---
 clang/lib/CodeGen/CGBuiltin.cpp | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index d57f491a20c8e..bff5451a01300 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -3829,14 +3829,18 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
       (E->getNumArgs() > 2) ? EmitScalarExpr(E->getArg(2)) : nullptr;
 
     Value *AlignmentValue = EmitScalarExpr(E->getArg(1));
-    ConstantInt *AlignmentCI = cast<ConstantInt>(AlignmentValue);
-    if (AlignmentCI->getValue().ugt(llvm::Value::MaximumAlignment))
-      AlignmentCI = ConstantInt::get(AlignmentCI->getIntegerType(),
-                                     llvm::Value::MaximumAlignment);
-
-    emitAlignmentAssumption(PtrValue, Ptr,
-                            /*The expr loc is sufficient.*/ SourceLocation(),
-                            AlignmentCI, OffsetValue);
+    if (ConstantInt *AlignmentCI = cast<ConstantInt>(AlignmentValue)) {
+      if (AlignmentCI->getValue().ugt(llvm::Value::MaximumAlignment))
+        AlignmentCI = ConstantInt::get(AlignmentCI->getIntegerType(),
+                                       llvm::Value::MaximumAlignment);
+
+      emitAlignmentAssumption(PtrValue, Ptr,
+                              /*The expr loc is sufficient.*/ SourceLocation(),
+                              AlignmentCI, OffsetValue);
+    } else
+      emitAlignmentAssumption(PtrValue, Ptr,
+                              /*The expr loc is sufficient.*/ SourceLocation(),
+                              AlignmentValue, OffsetValue);
     return RValue::get(PtrValue);
   }
   case Builtin::BI__builtin_assume_dereferenceable: {

>From eb5e0ed71165fcf90f0bfd54daa6642e4c17a0a4 Mon Sep 17 00:00:00 2001
From: Tang Jiajun <1220586548 at qq.com>
Date: Sat, 15 Feb 2025 01:17:26 +0800
Subject: [PATCH 3/3] Update builtin-assume-aligned.cpp

---
 clang/test/CodeGen/builtin-assume-aligned.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/clang/test/CodeGen/builtin-assume-aligned.cpp b/clang/test/CodeGen/builtin-assume-aligned.cpp
index fae4221d7d7e7..63ff01c98ccdc 100644
--- a/clang/test/CodeGen/builtin-assume-aligned.cpp
+++ b/clang/test/CodeGen/builtin-assume-aligned.cpp
@@ -3,12 +3,13 @@
 
 constexpr int get_align() { return 1; }
 
-// CHECK-LABEL: @Ztest1P(
+// CHECK-LABEL: @_Z5test1Pv(
 // CHECK-NEXT:  entry:
 // CHECK-NEXT:    [[A_ADDR:%.*]] = alloca ptr, align 8
 // CHECK-NEXT:    store ptr [[A:%.*]], ptr [[A_ADDR]], align 8
 // CHECK-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[A_ADDR]], align 8
-// CHECK-NEXT:    call void @llvm.assume(i1 true) [ "align"(ptr [[TMP0]], i64 32, i64 0) ]
+// CHECK-NEXT:    [[TMP1:%.*]] = call noundef i32 @_Z9get_alignv() 
+// CHECK-NEXT:    call void @llvm.assume(i1 true) [ "align"(ptr [[TMP0]], i64 32, i64 [[TMP1]]) ]
 // CHECK-NEXT:    store ptr [[TMP0]], ptr [[A_ADDR]], align 8
 // CHECK-NEXT:    [[TMP3:%.*]] = load ptr, ptr [[A_ADDR]], align 8
 // CHECK-NEXT:    [[ARRAYIDX:%.*]] = getelementptr inbounds i32, ptr [[TMP3]], i64 0