5c562f62a4
I noticed that the following case would compile in Clang but not GCC:
void *x(void) {
void *p = &&foo;
asm goto ("# %0\n\t# %l1":"+r"(p):::foo);
foo:;
return p;
}
Changing the output template above from %l2 would compile in GCC but not
Clang.
This demonstrates that when using tied outputs (say via the "+r" output
constraint), the hidden inputs occur or are numbered BEFORE the labels,
at least with GCC.
In fact, GCC does denote this in its documentation:
https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Extended-Asm.html#Goto-Labels
> Output operand with constraint modifier ‘+’ is counted as two operands
> because it is considered as one output and one input operand.
For the sake of compatibility, I think it's worthwhile to just make this
change.
It's better to use symbolic names for compatibility (especially now
between released version of Clang that support asm goto with outputs).
ie. %l1 from the above would be %l[foo]. The GCC docs also make this
recommendation.
Also, I cleaned up some cruft in GCCAsmStmt::getNamedOperand. AFAICT,
NumPlusOperands was no longer used, though I couldn't find which commit
didn't clean that up correctly.
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98096
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103640
Link: https://gcc.gnu.org/onlinedocs/gcc-11.2.0/gcc/Extended-Asm.html#Goto-Labels
Reviewed By: void
Differential Revision: https://reviews.llvm.org/D115471
132 lines
4.7 KiB
C
132 lines
4.7 KiB
C
// REQUIRES: x86-registered-target
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// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O0 -emit-llvm %s -o - | FileCheck %s
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// RUN: %clang_cc1 -triple i386-pc-linux-gnu -O0 -emit-llvm %s -o - | FileCheck %s
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int test1(int cond) {
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// CHECK-LABEL: define{{.*}} i32 @test1(
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// CHECK: callbr void asm sideeffect
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// CHECK: to label %asm.fallthrough [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough:
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asm volatile goto("testl %0, %0; jne %l1;" :: "r"(cond)::label_true, loop);
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asm volatile goto("testl %0, %0; jne %l2;" :: "r"(cond)::label_true, loop);
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// CHECK: callbr void asm sideeffect
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// CHECK: to label %asm.fallthrough1 [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough1:
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return 0;
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loop:
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return 0;
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label_true:
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return 1;
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}
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int test2(int cond) {
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// CHECK-LABEL: define{{.*}} i32 @test2(
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// CHECK: callbr i32 asm sideeffect
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// CHECK: to label %asm.fallthrough [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough:
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asm volatile goto("testl %0, %0; jne %l2;" : "=r"(cond) : "r"(cond) :: label_true, loop);
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asm volatile goto("testl %0, %0; jne %l3;" : "=r"(cond) : "r"(cond) :: label_true, loop);
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// CHECK: callbr i32 asm sideeffect
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// CHECK: to label %asm.fallthrough1 [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough1:
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return 0;
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loop:
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return 0;
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label_true:
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return 1;
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}
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int test3(int out1, int out2) {
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// CHECK-LABEL: define{{.*}} i32 @test3(
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// CHECK: callbr { i32, i32 } asm sideeffect
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// CHECK: to label %asm.fallthrough [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough:
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asm volatile goto("testl %0, %0; jne %l3;" : "=r"(out1), "=r"(out2) : "r"(out1) :: label_true, loop);
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asm volatile goto("testl %0, %0; jne %l4;" : "=r"(out1), "=r"(out2) : "r"(out1) :: label_true, loop);
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// CHECK: callbr { i32, i32 } asm sideeffect
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// CHECK: to label %asm.fallthrough2 [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough2:
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return 0;
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loop:
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return 0;
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label_true:
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return 1;
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}
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int test4(int out1, int out2) {
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// CHECK-LABEL: define{{.*}} i32 @test4(
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// CHECK: callbr { i32, i32 } asm sideeffect "jne ${5:l}", "={si},={di},r,0,1,i,i
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// CHECK: to label %asm.fallthrough [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough:
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if (out1 < out2)
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asm volatile goto("jne %l5" : "+S"(out1), "+D"(out2) : "r"(out1) :: label_true, loop);
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else
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asm volatile goto("jne %l7" : "+S"(out1), "+D"(out2) : "r"(out1), "r"(out2) :: label_true, loop);
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// CHECK: callbr { i32, i32 } asm sideeffect "jne ${7:l}", "={si},={di},r,r,0,1,i,i
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// CHECK: to label %asm.fallthrough2 [label %label_true, label %loop]
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// CHECK-LABEL: asm.fallthrough2:
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return out1 + out2;
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loop:
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return -1;
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label_true:
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return -2;
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}
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int test5(int addr, int size, int limit) {
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// CHECK-LABEL: define{{.*}} i32 @test5(
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// CHECK: callbr i32 asm "add $1,$0 ; jc ${4:l} ; cmp $2,$0 ; ja ${4:l} ; ", "=r,imr,imr,0,i
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// CHECK: to label %asm.fallthrough [label %t_err]
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// CHECK-LABEL: asm.fallthrough:
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asm goto(
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"add %1,%0 ; "
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"jc %l[t_err] ; "
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"cmp %2,%0 ; "
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"ja %l[t_err] ; "
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: "+r" (addr)
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: "g" (size), "g" (limit)
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: : t_err);
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return 0;
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t_err:
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return 1;
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}
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int test6(int out1) {
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// CHECK-LABEL: define{{.*}} i32 @test6(
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// CHECK: callbr i32 asm sideeffect "testl $0, $0; testl $1, $1; jne ${3:l}", "={si},r,0,i,i,{{.*}} i8* blockaddress(@test6, %label_true), i8* blockaddress(@test6, %landing)
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// CHECK: to label %asm.fallthrough [label %label_true, label %landing]
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// CHECK-LABEL: asm.fallthrough:
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// CHECK-LABEL: landing:
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int out2 = 42;
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asm volatile goto("testl %0, %0; testl %1, %1; jne %l3" : "+S"(out2) : "r"(out1) :: label_true, landing);
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landing:
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return out1 + out2;
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label_true:
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return -2;
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}
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// test7 - For the output templates in the asm string (%0, %l2), GCC places
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// hidden inputs tied to outputs ("+r" constraint) BEFORE labels. Test that foo
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// is $2 (or rather ${2:l} because of the l output template) in the emitted asm
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// string, not $1.
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void *test7(void) {
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// CHECK-LABEL: define{{.*}} i8* @test7(
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// CHECK: %1 = callbr i8* asm "# $0\0A\09# ${2:l}", "=r,0,i,~{dirflag},~{fpsr},~{flags}"(i8* %0, i8* blockaddress(@test7, %foo))
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// CHECK-NEXT: to label %asm.fallthrough [label %foo]
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void *p = &&foo;
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asm goto ("# %0\n\t# %l2":"+r"(p):::foo);
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foo:
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return p;
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}
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// test8 - the same as test7, but this time we use symbolic names rather than
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// numbered outputs.
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void *test8(void) {
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// CHECK-LABEL: define{{.*}} i8* @test8(
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// CHECK: %1 = callbr i8* asm "# $0\0A\09# ${2:l}", "=r,0,i,~{dirflag},~{fpsr},~{flags}"(i8* %0, i8* blockaddress(@test8, %foo))
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// CHECK-NEXT: to label %asm.fallthrough [label %foo]
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void *p = &&foo;
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asm goto ("# %0\n\t# %l[foo]":"+r"(p):::foo);
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foo:
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return p;
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}
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