158d72d728
Set the writable and dead_on_unwind attributes for sret arguments. These indicate that the argument points to writable memory (and it's legal to introduce spurious writes to it on entry to the function) and that the argument memory will not be used if the call unwinds. This enables additional MemCpyOpt/DSE/LICM optimizations.
71 lines
1.9 KiB
C
71 lines
1.9 KiB
C
// RUN: %clang_cc1 -triple i386-pc-elfiamcu -emit-llvm %s -o - | FileCheck %s
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// Structure that is more than 8 byte.
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struct Big {
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double a[10];
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};
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// Empty union with zero size must be returned as void.
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union U1 {
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} u1;
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// Too large union (80 bytes) must be returned via memory.
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union U2 {
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struct Big b;
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} u2;
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// Must be returned in register.
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union U3 {
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int x;
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} u3;
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// Empty struct with zero size, must be returned as void.
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struct S1 {
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} s1;
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// Must be returend in register.
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struct S2 {
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int x;
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} s2;
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// CHECK: [[UNION1_TYPE:%.+]] = type {}
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// CHECK: [[UNION2_TYPE:%.+]] = type { [[STRUCT_TYPE:%.+]] }
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// CHECK: [[STRUCT_TYPE]] = type { [10 x double] }
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// CHECK: [[UNION3_TYPE:%.+]] = type { i32 }
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// CHECK: [[STRUCT1_TYPE:%.+]] = type {}
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// CHECK: [[STRUCT2_TYPE:%.+]] = type { i32 }
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union U1 foo1(void) { return u1; }
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union U2 foo2(void) { return u2; }
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union U3 foo3(void) { return u3; }
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struct S1 bar1(void) { return s1; }
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struct S2 bar2(void) { return s2; }
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struct S1 bar3(union U1 u) { return s1; }
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// CHECK: define{{.*}} void @foo1()
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// CHECK: define{{.*}} void @foo2(ptr dead_on_unwind noalias writable sret([[UNION2_TYPE]]) align 4 %{{.+}})
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// CHECK: define{{.*}} i32 @foo3()
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// CHECK: define{{.*}} void @bar1()
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// CHECK: define{{.*}} i32 @bar2()
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// CHECK: define{{.*}} void @bar3()
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void run(void) {
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union U1 x1 = foo1();
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union U2 x2 = foo2();
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union U3 x3 = foo3();
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struct S1 y1 = bar1();
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struct S2 y2 = bar2();
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struct S1 y3 = bar3(x1);
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// CHECK: [[X1:%.+]] = alloca [[UNION1_TYPE]]
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// CHECK: [[X2:%.+]] = alloca [[UNION2_TYPE]]
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// CHECK: [[X3:%.+]] = alloca [[UNION3_TYPE]]
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// CHECK: [[Y1:%.+]] = alloca [[STRUCT1_TYPE]]
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// CHECK: [[Y2:%.+]] = alloca [[STRUCT2_TYPE]]
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// CHECK: call void @foo1()
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// CHECK: call void @foo2(ptr dead_on_unwind writable sret([[UNION2_TYPE]]) align 4 [[X2]])
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// CHECK: {{.+}} = call i32 @foo3()
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// CHECK: call void @bar1()
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// CHECK: {{.+}} = call i32 @bar2()
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// CHECK: call void @bar3()
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}
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