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Summary: Because GCC doesn't use $1 for code generation, inline assembly code can use $1 without having to add it to the clobbers list. LLVM, on the other hand, does not shy away from using $1, and this can cause conflicts with inline assembly which assumes GCC-like code generation. A solution to this problem is to make Clang automatically clobber $1 for all MIPS inline assembly. This is not the optimal solution, but it seems like a necessary compromise, for now. Reviewers: dsanders Reviewed By: dsanders Subscribers: cfe-commits Differential Revision: http://reviews.llvm.org/D6638 llvm-svn: 224428
27 lines
674 B
C
27 lines
674 B
C
// RUN: %clang -target mipsel-unknown-linux -S -o - -emit-llvm %s \
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// RUN: | FileCheck %s
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// This checks that the frontend will accept inline asm memory constraints.
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int foo()
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{
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// 'R': An address that can be used in a non-macro load or stor'
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// This test will result in the higher and lower nibbles being
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// switched due to the lwl/lwr instruction pairs.
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// CHECK: %{{[0-9]+}} = call i32 asm sideeffect "lwl $0, 1 + $1\0A\09lwr $0, 2 + $1\0A\09", "=r,*R,~{$1}"(i32* %{{[0-9,a-f]+}}) #1,
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int c = 0xffbbccdd;
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int *p = &c;
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int out = 0;
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__asm volatile (
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"lwl %0, 1 + %1\n\t"
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"lwr %0, 2 + %1\n\t"
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: "=r"(out)
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: "R"(*p)
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);
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return 0;
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}
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