llvm · fmayer · Nov 27, 2025 · Nov 19, 2025 · Nov 19, 2025 · Nov 20, 2025
diff --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1134,6 +1134,8 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
                   CodeGenOpts.SanitizeMinimalRuntime),
               /*MayReturn=*/
               CodeGenOpts.SanitizeRecover.has(SanitizerKind::LocalBounds),
+              /*HandlerPreserveAllRegs=*/
+              static_cast<bool>(CodeGenOpts.SanitizeHandlerPreserveAllRegs),
           };
         }
         FPM.addPass(BoundsCheckingPass(Options));

diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
@@ -3789,6 +3789,8 @@ static void emitCheckHandlerCall(CodeGenFunction &CGF,
   bool NeedsAbortSuffix =
       IsFatal && RecoverKind != CheckRecoverableKind::Unrecoverable;
   bool MinimalRuntime = CGF.CGM.getCodeGenOpts().SanitizeMinimalRuntime;
+  bool HandlerPreserveAllRegs =
+      CGF.CGM.getCodeGenOpts().SanitizeHandlerPreserveAllRegs;
   const SanitizerHandlerInfo &CheckInfo = SanitizerHandlers[CheckHandler];
   const StringRef CheckName = CheckInfo.Name;
   std::string FnName = "__ubsan_handle_" + CheckName.str();
@@ -3798,6 +3800,8 @@ static void emitCheckHandlerCall(CodeGenFunction &CGF,
     FnName += "_minimal";
   if (NeedsAbortSuffix)
     FnName += "_abort";
+  else if (MinimalRuntime && HandlerPreserveAllRegs)
+    FnName += "_preserve";
   bool MayReturn =
       !IsFatal || RecoverKind == CheckRecoverableKind::AlwaysRecoverable;
 
@@ -3818,6 +3822,10 @@ static void emitCheckHandlerCall(CodeGenFunction &CGF,
             (CGF.CurCodeDecl && CGF.CurCodeDecl->hasAttr<OptimizeNoneAttr>());
   if (NoMerge)
     HandlerCall->addFnAttr(llvm::Attribute::NoMerge);
+  if (MinimalRuntime && HandlerPreserveAllRegs) {
+    // N.B. there is also a clang::CallingConv which is not what we want here.
+    HandlerCall->setCallingConv(llvm::CallingConv::PreserveAll);
+  }
   if (!MayReturn) {
     HandlerCall->setDoesNotReturn();
     CGF.Builder.CreateUnreachable();

diff --git a/clang/test/CodeGen/cfi-icall-trap-recover-runtime.c b/clang/test/CodeGen/cfi-icall-trap-recover-runtime.c
@@ -9,6 +9,9 @@
 
 // RUN: %clang_cc1 -fsanitize=cfi-icall -fno-sanitize-trap=cfi-icall -fsanitize-recover=cfi-icall -fsanitize-minimal-runtime -flto -fvisibility=hidden -triple x86_64-unknown-linux -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=RECOVER_MIN %s
 
+// RUN: %clang_cc1 -fsanitize=cfi-icall -fno-sanitize-trap=cfi-icall -fsanitize-recover=cfi-icall -fsanitize-minimal-runtime -fsanitize-handler-preserve-all-regs -flto -fvisibility=hidden -triple x86_64-unknown-linux -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=PRESERVE_MIN %s
+
+
 // TRAP-LABEL: define hidden void @f(
 // TRAP-SAME: ) #[[ATTR0:[0-9]+]] !type [[META6:![0-9]+]] !type [[META7:![0-9]+]] {
 // TRAP-NEXT:  [[ENTRY:.*:]]
@@ -34,6 +37,11 @@
 // RECOVER_MIN-NEXT:  [[ENTRY:.*:]]
 // RECOVER_MIN-NEXT:    ret void
 //
+// PRESERVE_MIN-LABEL: define hidden void @f(
+// PRESERVE_MIN-SAME: ) #[[ATTR0:[0-9]+]] !type [[META6:![0-9]+]] !type [[META7:![0-9]+]] {
+// PRESERVE_MIN-NEXT:  [[ENTRY:.*:]]
+// PRESERVE_MIN-NEXT:    ret void
+//
 void f() {
 }
 
@@ -146,6 +154,27 @@ void xf();
 // RECOVER_MIN-NEXT:    call void (...) [[TMP2]]()
 // RECOVER_MIN-NEXT:    ret void
 //
+// PRESERVE_MIN-LABEL: define hidden void @g(
+// PRESERVE_MIN-SAME: i32 noundef [[B:%.*]]) #[[ATTR0]] !type [[META8:![0-9]+]] !type [[META9:![0-9]+]] {
+// PRESERVE_MIN-NEXT:  [[ENTRY:.*:]]
+// PRESERVE_MIN-NEXT:    [[B_ADDR:%.*]] = alloca i32, align 4
+// PRESERVE_MIN-NEXT:    [[FP:%.*]] = alloca ptr, align 8
+// PRESERVE_MIN-NEXT:    store i32 [[B]], ptr [[B_ADDR]], align 4
+// PRESERVE_MIN-NEXT:    [[TMP0:%.*]] = load i32, ptr [[B_ADDR]], align 4
+// PRESERVE_MIN-NEXT:    [[TOBOOL:%.*]] = icmp ne i32 [[TMP0]], 0
+// PRESERVE_MIN-NEXT:    [[TMP1:%.*]] = zext i1 [[TOBOOL]] to i64
+// PRESERVE_MIN-NEXT:    [[COND:%.*]] = select i1 [[TOBOOL]], ptr @f, ptr @xf
+// PRESERVE_MIN-NEXT:    store ptr [[COND]], ptr [[FP]], align 8
+// PRESERVE_MIN-NEXT:    [[TMP2:%.*]] = load ptr, ptr [[FP]], align 8
+// PRESERVE_MIN-NEXT:    [[TMP3:%.*]] = call i1 @llvm.type.test(ptr [[TMP2]], metadata !"_ZTSFvE"), !nosanitize [[META10:![0-9]+]]
+// PRESERVE_MIN-NEXT:    br i1 [[TMP3]], label %[[CONT:.*]], label %[[HANDLER_CFI_CHECK_FAIL:.*]], !prof [[PROF11:![0-9]+]], !nosanitize [[META10]]
+// PRESERVE_MIN:       [[HANDLER_CFI_CHECK_FAIL]]:
+// PRESERVE_MIN-NEXT:    call preserve_allcc void @__ubsan_handle_cfi_check_fail_minimal_preserve() #[[ATTR4:[0-9]+]], !nosanitize [[META10]]
+// PRESERVE_MIN-NEXT:    br label %[[CONT]], !nosanitize [[META10]]
+// PRESERVE_MIN:       [[CONT]]:
+// PRESERVE_MIN-NEXT:    call void (...) [[TMP2]]()
+// PRESERVE_MIN-NEXT:    ret void
+//
 void g(int b) {
   void (*fp)() = b ? f : xf;
   fp();
@@ -186,3 +215,10 @@ void g(int b) {
 // RECOVER_MIN: [[META10]] = !{}
 // RECOVER_MIN: [[PROF11]] = !{!"branch_weights", i32 1048575, i32 1}
 //.
+// PRESERVE_MIN: [[META6]] = !{i64 0, !"_ZTSFvE"}
+// PRESERVE_MIN: [[META7]] = !{i64 0, !"_ZTSFvE.generalized"}
+// PRESERVE_MIN: [[META8]] = !{i64 0, !"_ZTSFviE"}
+// PRESERVE_MIN: [[META9]] = !{i64 0, !"_ZTSFviE.generalized"}
+// PRESERVE_MIN: [[META10]] = !{}
+// PRESERVE_MIN: [[PROF11]] = !{!"branch_weights", i32 1048575, i32 1}
+//.
diff --git a/clang/test/CodeGenCXX/cfi-vcall-trap-recover-runtime.cpp b/clang/test/CodeGenCXX/cfi-vcall-trap-recover-runtime.cpp
@@ -9,6 +9,8 @@
 
 // RUN: %clang_cc1 -fsanitize=cfi-vcall -fno-sanitize-trap=cfi-vcall -fsanitize-recover=cfi-vcall -fsanitize-minimal-runtime -flto -fvisibility=hidden -triple x86_64-unknown-linux -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=RECOVER_MIN %s
 
+// RUN: %clang_cc1 -fsanitize=cfi-vcall -fno-sanitize-trap=cfi-vcall -fsanitize-recover=cfi-vcall -fsanitize-minimal-runtime -flto -fvisibility=hidden -triple x86_64-unknown-linux -fwhole-program-vtables -fsanitize-handler-preserve-all-regs -emit-llvm -o - %s | FileCheck --check-prefix=PRESERVE_MIN %s
+
 struct S1 {
   virtual void f();
 };
@@ -111,6 +113,25 @@ struct S1 {
 // RECOVER_MIN-NEXT:    call void [[TMP3]](ptr noundef nonnull align 8 dereferenceable(8) [[TMP0]])
 // RECOVER_MIN-NEXT:    ret void
 //
+// PRESERVE_MIN-LABEL: define hidden void @_Z3s1fP2S1(
+// PRESERVE_MIN-SAME: ptr noundef [[S1:%.*]]) #[[ATTR0:[0-9]+]] {
+// PRESERVE_MIN-NEXT:  [[ENTRY:.*:]]
+// PRESERVE_MIN-NEXT:    [[S1_ADDR:%.*]] = alloca ptr, align 8
+// PRESERVE_MIN-NEXT:    store ptr [[S1]], ptr [[S1_ADDR]], align 8
+// PRESERVE_MIN-NEXT:    [[TMP0:%.*]] = load ptr, ptr [[S1_ADDR]], align 8
+// PRESERVE_MIN-NEXT:    [[VTABLE:%.*]] = load ptr, ptr [[TMP0]], align 8
+// PRESERVE_MIN-NEXT:    [[TMP1:%.*]] = call i1 @llvm.type.test(ptr [[VTABLE]], metadata !"_ZTS2S1"), !nosanitize [[META5:![0-9]+]]
+// PRESERVE_MIN-NEXT:    [[TMP2:%.*]] = call i1 @llvm.type.test(ptr [[VTABLE]], metadata !"all-vtables"), !nosanitize [[META5]]
+// PRESERVE_MIN-NEXT:    br i1 [[TMP1]], label %[[CONT:.*]], label %[[HANDLER_CFI_CHECK_FAIL:.*]], !prof [[PROF6:![0-9]+]], !nosanitize [[META5]]
+// PRESERVE_MIN:       [[HANDLER_CFI_CHECK_FAIL]]:
+// PRESERVE_MIN-NEXT:    call preserve_allcc void @__ubsan_handle_cfi_check_fail_minimal_preserve() #[[ATTR3:[0-9]+]], !nosanitize [[META5]]
+// PRESERVE_MIN-NEXT:    br label %[[CONT]], !nosanitize [[META5]]
+// PRESERVE_MIN:       [[CONT]]:
+// PRESERVE_MIN-NEXT:    [[VFN:%.*]] = getelementptr inbounds ptr, ptr [[VTABLE]], i64 0
+// PRESERVE_MIN-NEXT:    [[TMP3:%.*]] = load ptr, ptr [[VFN]], align 8
+// PRESERVE_MIN-NEXT:    call void [[TMP3]](ptr noundef nonnull align 8 dereferenceable(8) [[TMP0]])
+// PRESERVE_MIN-NEXT:    ret void
+//
 void s1f(S1 *s1) {
   s1->f();
 }
@@ -130,3 +151,6 @@ void s1f(S1 *s1) {
 // RECOVER_MIN: [[META5]] = !{}
 // RECOVER_MIN: [[PROF6]] = !{!"branch_weights", i32 1048575, i32 1}
 //.
+// PRESERVE_MIN: [[META5]] = !{}
+// PRESERVE_MIN: [[PROF6]] = !{!"branch_weights", i32 1048575, i32 1}
+//.
diff --git a/compiler-rt/test/ubsan_minimal/TestCases/override-callback.c b/compiler-rt/test/ubsan_minimal/TestCases/override-callback.c
@@ -1,4 +1,5 @@
 // RUN: %clang_min_runtime -fsanitize=implicit-integer-sign-change                                        %s -o %t &&             %run %t 2>&1 | FileCheck %s
+// RUN: %clang_min_runtime -fsanitize=implicit-integer-sign-change -fsanitize-handler-preserve-all-regs   %s -o %t &&             %run %t 2>&1 | FileCheck %s --check-prefixes=PRESERVE
 // RUN: %clang_min_runtime -fsanitize=implicit-integer-sign-change -fno-sanitize-recover=all              %s -o %t && not --crash %run %t 2>&1 | FileCheck %s
 // RUN: %clang_min_runtime -fsanitize=implicit-integer-sign-change -fno-sanitize-recover=all -DOVERRIDE=1 %s -o %t && not --crash %run %t 2>&1 | FileCheck %s --check-prefixes=FATAL
 
@@ -12,6 +13,11 @@ void __ubsan_report_error(const char *kind, uintptr_t caller) {
   fprintf(stderr, "CUSTOM_CALLBACK: %s\n", kind);
 }
 
+[[clang::preserve_all]] void __ubsan_report_error_preserve(const char *kind,
+                                                           uintptr_t caller) {
+  fprintf(stderr, "CUSTOM_CALLBACK_PRESERVE: %s\n", kind);
+}
+
 #if OVERRIDE
 void __ubsan_report_error_fatal(const char *kind, uintptr_t caller) {
   fprintf(stderr, "FATAL_CALLBACK: %s\n", kind);
@@ -21,5 +27,6 @@ void __ubsan_report_error_fatal(const char *kind, uintptr_t caller) {
 int main(int argc, const char **argv) {
   int32_t t0 = (~((uint32_t)0));
   // CHECK: CUSTOM_CALLBACK: implicit-conversion
+  // PRESERVE: CUSTOM_CALLBACK_PRESERVE: implicit-conversion
   // FATAL: FATAL_CALLBACK: implicit-conversion
 }
diff --git a/llvm/include/llvm/Transforms/Instrumentation/BoundsChecking.h b/llvm/include/llvm/Transforms/Instrumentation/BoundsChecking.h
@@ -23,10 +23,12 @@ class BoundsCheckingPass : public PassInfoMixin<BoundsCheckingPass> {
 public:
   struct Options {
     struct Runtime {
-      Runtime(bool MinRuntime, bool MayReturn)
-          : MinRuntime(MinRuntime), MayReturn(MayReturn) {}
+      Runtime(bool MinRuntime, bool MayReturn, bool HandlerPreserveAllRegs)
+          : MinRuntime(MinRuntime), MayReturn(MayReturn),
+            HandlerPreserveAllRegs(HandlerPreserveAllRegs) {}
       bool MinRuntime;
       bool MayReturn;
+      bool HandlerPreserveAllRegs;
     };
     std::optional<Runtime> Rt; // Trap if empty.
     bool Merge = false;

diff --git a/llvm/lib/Passes/PassBuilder.cpp b/llvm/lib/Passes/PassBuilder.cpp
@@ -1590,21 +1590,31 @@ parseBoundsCheckingOptions(StringRef Params) {
       Options.Rt = {
           /*MinRuntime=*/false,
           /*MayReturn=*/true,
+          /*HandlerPreserveAllRegs=*/false,
       };
     } else if (ParamName == "rt-abort") {
       Options.Rt = {
           /*MinRuntime=*/false,
           /*MayReturn=*/false,
+          /*HandlerPreserveAllRegs=*/false,
       };
     } else if (ParamName == "min-rt") {
       Options.Rt = {
           /*MinRuntime=*/true,
           /*MayReturn=*/true,
+          /*HandlerPreserveAllRegs=*/false,
+      };
+    } else if (ParamName == "min-rt-handler-preserve-all-regs") {
+      Options.Rt = {
+          /*MinRuntime=*/true,
+          /*MayReturn=*/true,
+          /*HandlerPreserveAllRegs=*/true,
       };
     } else if (ParamName == "min-rt-abort") {
       Options.Rt = {
           /*MinRuntime=*/true,
           /*MayReturn=*/false,
+          /*HandlerPreserveAllRegs=*/false,
       };
     } else if (ParamName == "merge") {
       Options.Merge = true;

diff --git a/llvm/lib/Transforms/Instrumentation/BoundsChecking.cpp b/llvm/lib/Transforms/Instrumentation/BoundsChecking.cpp
@@ -178,6 +178,8 @@ getRuntimeCallName(const BoundsCheckingPass::Options::Runtime &Opts) {
     Name += "_minimal";
   if (!Opts.MayReturn)
     Name += "_abort";
+  else if (Opts.HandlerPreserveAllRegs && Opts.MinRuntime)
+    Name += "_preserve";
   return Name;
 }
 

diff --git a/llvm/test/Instrumentation/BoundsChecking/runtimes.ll b/llvm/test/Instrumentation/BoundsChecking/runtimes.ll
@@ -8,6 +8,7 @@
 ; RUN: opt < %s -passes='bounds-checking<rt-abort>'     -S | FileCheck %s --check-prefixes=RTABORT-NOMERGE
 ; RUN: opt < %s -passes='bounds-checking<min-rt>'       -S | FileCheck %s --check-prefixes=MINRT-NOMERGE
 ; RUN: opt < %s -passes='bounds-checking<min-rt-abort>' -S | FileCheck %s --check-prefixes=MINRTABORT-NOMERGE
+; RUN: opt < %s -passes='bounds-checking<min-rt-handler-preserve-all-regs>' -S | FileCheck %s --check-prefixes=MINRT-PRESERVE-NOMERGE
 ;
 ; RUN: opt < %s -passes='bounds-checking<trap;guard=3>'   -S | FileCheck %s --check-prefixes=TR-GUARD-COMMON,TR-GUARD-THREE
 ; RUN: opt < %s -passes='bounds-checking<trap;guard=13>'   -S | FileCheck %s --check-prefixes=TR-GUARD-COMMON,TR-GUARD-THIRTEEN
@@ -111,6 +112,22 @@ define void @f1(i64 %x) nounwind {
 ; MINRT-NOMERGE-NEXT:    call void @__ubsan_handle_local_out_of_bounds_minimal() #[[ATTR1:[0-9]+]], !nosanitize [[META0]]
 ; MINRT-NOMERGE-NEXT:    br label %[[BB7]], !nosanitize [[META0]]
 ;
+; MINRT-PRESERVE-NOMERGE-LABEL: define void @f1(
+; MINRT-PRESERVE-NOMERGE-SAME: i64 [[X:%.*]]) #[[ATTR0:[0-9]+]] {
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP1:%.*]] = mul i64 16, [[X]]
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP2:%.*]] = alloca i128, i64 [[X]], align 8
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP3:%.*]] = sub i64 [[TMP1]], 0, !nosanitize [[META0:![0-9]+]]
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP4:%.*]] = icmp ult i64 [[TMP3]], 16, !nosanitize [[META0]]
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP5:%.*]] = or i1 false, [[TMP4]], !nosanitize [[META0]]
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP6:%.*]] = or i1 false, [[TMP5]], !nosanitize [[META0]]
+; MINRT-PRESERVE-NOMERGE-NEXT:    br i1 [[TMP6]], label %[[TRAP:.*]], label %[[BB7:.*]]
+; MINRT-PRESERVE-NOMERGE:       [[BB7]]:
+; MINRT-PRESERVE-NOMERGE-NEXT:    [[TMP8:%.*]] = load i128, ptr [[TMP2]], align 4
+; MINRT-PRESERVE-NOMERGE-NEXT:    ret void
+; MINRT-PRESERVE-NOMERGE:       [[TRAP]]:
+; MINRT-PRESERVE-NOMERGE-NEXT:    call void @__ubsan_handle_local_out_of_bounds_minimal_preserve() #[[ATTR1:[0-9]+]], !nosanitize [[META0]]
+; MINRT-PRESERVE-NOMERGE-NEXT:    br label %[[BB7]], !nosanitize [[META0]]
+;
 ; MINRTABORT-NOMERGE-LABEL: define void @f1(
 ; MINRTABORT-NOMERGE-SAME: i64 [[X:%.*]]) #[[ATTR0:[0-9]+]] {
 ; MINRTABORT-NOMERGE-NEXT:    [[TMP1:%.*]] = mul i64 16, [[X]]