[PATCH] [ASan] Don't use stack malloc for 32-bit functions using inline asm

[Reid Kleckner]

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D8790

Files:
  llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
  llvm/trunk/test/Instrumentation/AddressSanitizer/X86/asm_cpuid.ll

Index: llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -1766,9 +1766,11 @@
   uint64_t LocalStackSize = L.FrameSize;
   bool DoStackMalloc =
       ClUseAfterReturn && LocalStackSize <= kMaxStackMallocSize;
-  // Don't do dynamic alloca in presence of inline asm: too often it
-  // makes assumptions on which registers are available.
+  // Don't do dynamic alloca in presence of inline asm: too often it makes
+  // assumptions on which registers are available. Don't do stack malloc in the
+  // presence of inline asm on 32-bit platforms for the same reason.
   bool DoDynamicAlloca = ClDynamicAllocaStack && !HasNonEmptyInlineAsm;
+  DoStackMalloc &= !HasNonEmptyInlineAsm || ASan.LongSize != 32;
 
   Value *StaticAlloca =
       DoDynamicAlloca ? nullptr : createAllocaForLayout(IRB, L, false);
Index: llvm/trunk/test/Instrumentation/AddressSanitizer/X86/asm_cpuid.ll
===================================================================
--- llvm/trunk/test/Instrumentation/AddressSanitizer/X86/asm_cpuid.ll
+++ llvm/trunk/test/Instrumentation/AddressSanitizer/X86/asm_cpuid.ll
@@ -0,0 +1,53 @@
+; RUN: opt < %s -asan -S -o %t.ll
+; RUN: FileCheck %s < %t.ll
+; RUN: llc < %t.ll | FileCheck %s --check-prefix=ASM
+
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-S32"
+target triple = "i386-pc-windows-msvc"
+
+define void @MyCPUID(i32 %fxn, i32* %out) sanitize_address {
+  %fxn.ptr = alloca i32
+  %a.ptr = alloca i32
+  %b.ptr = alloca i32
+  %c.ptr = alloca i32
+  %d.ptr = alloca i32
+  store i32 %fxn, i32* %fxn.ptr
+  call void asm sideeffect inteldialect "xchg ebx, esi\0A\09mov eax, dword ptr $4\0A\09cpuid\0A\09mov dword ptr $0, eax\0A\09mov dword ptr $1, ebx\0A\09mov dword ptr $2, ecx\0A\09mov dword ptr $3, edx\0A\09xchg ebx, esi", "=*m,=*m,=*m,=*m,*m,~{eax},~{ebx},~{ecx},~{edx},~{esi},~{dirflag},~{fpsr},~{flags}"(i32* %a.ptr, i32* %b.ptr, i32* %c.ptr, i32* %d.ptr, i32* %fxn.ptr)
+
+  %a = load i32, i32* %a.ptr
+  %a.out = getelementptr inbounds i32, i32* %out, i32 0
+  store i32 %a, i32* %a.out
+
+  %b = load i32, i32* %b.ptr
+  %b.out = getelementptr inbounds i32, i32* %out, i32 1
+  store i32 %b, i32* %b.out
+
+  %c = load i32, i32* %c.ptr
+  %c.out = getelementptr inbounds i32, i32* %out, i32 2
+  store i32 %c, i32* %c.out
+
+  %d = load i32, i32* %d.ptr
+  %d.out = getelementptr inbounds i32, i32* %out, i32 3
+  store i32 %d, i32* %d.out
+
+  ret void
+}
+
+; We used to introduce stack mallocs for UAR detection, but that makes LLVM run
+; out of registers on 32-bit platforms. Therefore, we don't do stack malloc on
+; such functions.
+
+; CHECK-LABEL: define void @MyCPUID(i32 %fxn, i32* %out)
+; CHECK: %MyAlloca = alloca [96 x i8], align 32
+; CHECK-NOT: call {{.*}} @__asan_stack_malloc
+
+; The code generator should recognize that all operands are just stack memory.
+; This is important with MS inline asm where operand lists are implicit and all
+; local variables can be referenced freely.
+
+; ASM-LABEL: MyCPUID:
+; ASM:      cpuid
+; ASM-NEXT: movl    %eax, {{[0-9]+}}(%esp)
+; ASM-NEXT: movl    %ebx, {{[0-9]+}}(%esp)
+; ASM-NEXT: movl    %ecx, {{[0-9]+}}(%esp)
+; ASM-NEXT: movl    %edx, {{[0-9]+}}(%esp)

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