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50cac24877
Summary: Clang's "asm goto" feature didn't initially support outputs constraints. That was the same behavior as gcc's implementation. The decision by gcc not to support outputs was based on a restriction in their IR regarding terminators. LLVM doesn't restrict terminators from returning values (e.g. 'invoke'), so it made sense to support this feature. Output values are valid only on the 'fallthrough' path. If an output value's used on an indirect branch, then it's 'poisoned'. In theory, outputs *could* be valid on the 'indirect' paths, but it's very difficult to guarantee that the original semantics would be retained. E.g. because indirect labels could be used as data, we wouldn't be able to split critical edges in situations where two 'callbr' instructions have the same indirect label, because the indirect branch's destination would no longer be the same. Reviewers: jyknight, nickdesaulniers, hfinkel Reviewed By: jyknight, nickdesaulniers Subscribers: MaskRay, rsmith, hiraditya, llvm-commits, cfe-commits, craig.topper, rnk Tags: #clang, #llvm Differential Revision: https://reviews.llvm.org/D69876
90 lines
3.0 KiB
C++
90 lines
3.0 KiB
C++
// RUN: %clang_cc1 -triple i386-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s
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// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s
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int a, b, c, d, e, f, g, h, i, j, k, l;
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void test1(void) {
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__asm__ volatile goto (""
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:: [a] "r" (a), [b] "r" (b), [c] "r" (c), [d] "r" (d),
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[e] "r" (e), [f] "r" (f), [g] "r" (g), [h] "r" (h),
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[i] "r" (i), [j] "r" (j), [k] "r" (k), [l] "r" (l)
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::lab1,lab2);
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lab1: return;
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lab2: return;
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}
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void test2(void) {
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__asm__ volatile goto (""
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:: [a] "r,m" (a), [b] "r,m" (b), [c] "r,m" (c), [d] "r,m" (d),
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[e] "r,m" (e), [f] "r,m" (f), [g] "r,m" (g), [h] "r,m" (h),
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[i] "r,m" (i), [j] "r,m" (j), [k] "r,m" (k), [l] "r,m" (l)
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:: lab);
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lab: return;
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}
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int test3(int x) {
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__asm__ volatile goto ("decl %0; jnz %l[a]"
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: "=r" (x) : "m" (x) : "memory" : a);
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a:
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return -x;
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}
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int test4(int x) {
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int y;
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if (x > 42)
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__asm__ volatile goto ("decl %0; jnz %l[a]"
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: "=r" (x), "=r" (y) : "m" (x) : "memory" : a);
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else
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__asm__ volatile goto ("decl %0; jnz %l[b]"
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: "=r" (x), "=r" (y) : "m" (x) : "memory" : b);
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x = y + 42;
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a:
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return -x;
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b:
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return +x;
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}
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int test5(void) {
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int x,cond,*e;
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// expected-error@+1 {{expected ')'}}
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asm ("mov %[e], %[e]" : : [e] "rm" (*e)::a)
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// expected-error@+1 {{expected identifier}}
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asm goto ("decl %0;" :: "m"(x) : "memory" : );
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// expected-error@+1 {{expected ':'}}
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asm goto ("decl %0;" :: "m"(x) : "memory" );
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// expected-error@+1 {{use of undeclared label 'x'}}
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asm goto ("decl %0;" :: "m"(x) : "memory" :x);
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// expected-error@+1 {{use of undeclared label 'b'}}
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asm goto ("decl %0;" :: "m"(x) : "memory" :b);
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// expected-error@+1 {{invalid operand number in inline asm string}}
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asm goto ("testl %0, %0; jne %l3;" :: "r"(cond)::label_true, loop);
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// expected-error@+1 {{unknown symbolic operand name in inline assembly string}}
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asm goto ("decl %0; jnz %l[b]" :: "m"(x) : "memory" : a);
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label_true:
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loop:
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a:
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return 0;
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}
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int test6(int y) {
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int x,cond,*e;
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// expected-error@+1 {{expected ')'}}
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asm ("mov %[e], %[e]" : "=r" (y) : [e] "rm" (*e), "r" (y) :: a)
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// expected-error@+1 {{expected identifier}}
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asm goto ("decl %0;" : "=r" (y) : "m" (x), "r" (y) : "memory" :);
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// expected-error@+1 {{expected ':'}}
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asm goto ("decl %0;" : "=r" (y) : "m" (x), "r" (y) : "memory");
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// expected-error@+1 {{use of undeclared label 'x'}}
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asm goto ("decl %0;" : "=r" (y) : "m" (x), "r" (y) : "memory" : x);
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// expected-error@+1 {{use of undeclared label 'b'}}
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asm goto ("decl %0;" : "=r" (y) : "m" (x), "r" (y) : "memory" : b);
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// expected-error@+1 {{invalid operand number in inline asm string}}
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asm goto ("testl %0, %0; jne %l5;" : "=r" (y) : "r" (cond), "r" (y) :: label_true, loop);
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// expected-error@+1 {{unknown symbolic operand name in inline assembly string}}
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asm goto ("decl %0; jnz %l[b]" : "=r" (y) : "m" (x), "r" (y) : "memory" : a);
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label_true:
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loop:
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a:
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return 0;
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}
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