96ab74bf17
Extend `isAllocSiteRemovable` to be able to check if the ModRef info indicates the alloca is only Ref or only Mod, and be able to remove it accordingly. It seemed that there were a surprising number of benchmarks with this pattern which weren't getting optimized previously (due to MemorySSA walk limits). There were somewhat more existing tests than I'd like to have modified which were simply doing exactly this pattern (and thus relying on undef memory). Claude code contributed the new tests (and found an important typo that I'd made). This implements the discussion in https://github.com/llvm/llvm-project/pull/143782#discussion_r2142720376.
38 lines
1.1 KiB
C
38 lines
1.1 KiB
C
// This tests loop unrolling and loop deletion (enabled under -O1)
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// RUN: %clang_cc1 -std=c11 -O1 -fno-unroll-loops -o - %s -emit-llvm | FileCheck %s
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// RUN: %clang_cc1 -std=c99 -O1 -fno-unroll-loops -o - %s -emit-llvm | FileCheck %s --check-prefix C99
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extern int a[16];
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int b = 0;
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int foo(void) {
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#pragma unroll
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for (int i = 0; i < 16; ++i)
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a[i] = b += 2;
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return b;
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}
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// Check br i1 to make sure that the loop is fully unrolled
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// CHECK-LABEL: foo
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// CHECK-NOT: br i1
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void Helper(void) {
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const int *nodes[5] = {0};
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int num_active = 5;
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while (num_active)
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#pragma clang loop unroll(full)
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for (int i = 0; i < 5; ++i)
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if (nodes[i])
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--num_active;
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}
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// Check br i1 to make sure the loop is gone, there will still be a label branch for the infinite loop.
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// In C99, there was no forward progress requirement, so we expect the infinite loop to still exist,
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// but for C11 and onwards, the infinite loop can be deleted.
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// CHECK-LABEL: Helper
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// C99: br label
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// C99-NOT: br i1
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// C99: br label
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// CHECK: entry:
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// CHECK-NOT: br i1
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// CHECK-NEXT: ret void
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