[PATCH] D12181: [sanitizer] Add -fsanitize-trap-function.

[Josh Gao via cfe-commits]

jmgao added a comment.

With #1, it seems unfortunate to not be able to distinguish between a sanitize inserted __builtin_trap and code manually calling it. (Would there be an -fsanitize-trap=trap? :-)
With #2, we're worried about the generated code being noticeably worse in the unexceptional case than running without the sanitizers.

Compiling the following snippet with -O3 -fsanitize=unsigned-integer-overflow -fomit-frame-pointer and additional arguments generates:

  unsigned foo(unsigned a, unsigned b, unsigned c, unsigned d) { return a + b + c + d; }

no additional arguments

  foo:
  	push	{r4, r5, r6, r7, r8, lr}
  	mov	r5, r2
  	mov	r2, r1
  	mov	r1, r0
  	mov	r0, #1
  	mov	r8, r3
  	mov	r4, #1
  	add	r6, r1, r2
  	cmp	r6, r1
  	movhs	r0, #0
  	cmp	r0, #0
  	bne	.LBB0_4
  .LBB0_1:
  	add	r7, r6, r5
  	cmp	r7, r6
  	movhs	r4, #0
  	cmp	r4, #0
  	bne	.LBB0_5
  .LBB0_2:
  	add	r5, r7, r8
  	mov	r0, #1
  	cmp	r5, r7
  	movhs	r0, #0
  	cmp	r0, #0
  	bne	.LBB0_6
  .LBB0_3:
  	mov	r0, r5
  	pop	{r4, r5, r6, r7, r8, lr}
  	bx	lr
  .LBB0_4:
          <overflow handling>

-fsanitize-trap=unsigned-integer-overflow

  foo:
  	add	r1, r0, r1
  	mov	r12, #1
  	cmp	r1, r0
  	mov	r0, #1
  	movhs	r0, #0
  	cmp	r0, #0
  	bne	.LBB0_3
  @ BB#1:
  	add	r2, r1, r2
  	cmp	r2, r1
  	movhs	r12, #0
  	cmp	r12, #0
  	bne	.LBB0_3
  @ BB#2:
  	add	r0, r2, r3
  	mov	r1, #1
  	cmp	r0, r2
  	movhs	r1, #0
  	cmp	r1, #0
  	bxeq	lr
  .LBB0_3:
  	.long	3892305662              @ trap

-fsanitize-trap=unsigned-integer-overflow -fsanitize-trap-function=sanitize_trap

  foo:
  	push	{r11, lr}      ; Not quite perfect, but still better
  	add	r1, r0, r1
  	mov	r12, #1
  	cmp	r1, r0
  	mov	r0, #1
  	movhs	r0, #0
  	cmp	r0, #0
  	bne	.LBB0_3
  @ BB#1:
  	add	r2, r1, r2
  	cmp	r2, r1
  	movhs	r12, #0
  	cmp	r12, #0
  	bne	.LBB0_3
  @ BB#2:
  	add	r0, r2, r3
  	mov	r1, #1
  	cmp	r0, r2
  	movhs	r1, #0
  	cmp	r1, #0
  	popeq	{r11, lr}
  	bxeq	lr
  .LBB0_3:
  	bl	sanitize_trap(PLT)


http://reviews.llvm.org/D12181