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Since C++11, the C++ standard has a forward progress guarantee [intro.progress], so all such functions must have the `mustprogress` requirement. In addition, from C11 and onwards, loops without a non-zero constant conditional or no conditional are also required to make progress (C11 6.8.5p6). This patch implements these attribute deductions so they can be used by the optimization passes. Differential Revision: https://reviews.llvm.org/D86841
38 lines
1.0 KiB
C++
38 lines
1.0 KiB
C++
// RUN: %clang_cc1 -emit-llvm %s -o - | FileCheck %s
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// We expect to get a loop structure like this:
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// do.body: ; preds = %do.cond, ...
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// ...
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// br label %do.cond
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// do.cond: ; preds = %do.body
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// ...
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// br i1 %cmp, label %do.body, label %do.end
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// do.end: ; preds = %do.cond
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// ...
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//
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// Verify that the loop metadata only is put on the backedge.
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//
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// CHECK-NOT: llvm.loop
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// CHECK-LABEL: do.cond:
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// CHECK: br {{.*}}, label %do.body, label %do.end, !llvm.loop ![[LMD1:[0-9]+]]
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// CHECK-LABEL: do.end:
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// CHECK-NOT: llvm.loop
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// CHECK: ![[LMD1]] = distinct !{![[LMD1]], [[LMD2:![0-9]+]], ![[LMD3:[0-9]+]]}
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// CHECK: [[LMD2]] = !{!"llvm.loop.mustprogress"}
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// CHECK: ![[LMD3]] = !{!"llvm.loop.unroll.count", i32 4}
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int test(int a[], int n) {
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int i = 0;
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int sum = 0;
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#pragma unroll 4
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do
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{
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a[i] = a[i] + 1;
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sum = sum + a[i];
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i++;
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} while (i < n);
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return sum;
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}
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