[flang-commits] [clang] [flang] [flang] Add -f[no-]unroll-loops flag (PR #122906)

[David Truby via flang-commits]

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@@ -0,0 +1,37 @@
+! RUN: %flang_fc1 -emit-llvm -O1 -funroll-loops -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,UNROLL
+! RUN: %flang_fc1 -emit-llvm -O2 -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,UNROLL
+! RUN: %flang_fc1 -emit-llvm -O1 -fno-unroll-loops -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,NO-UNROLL
+! RUN: %flang_fc1 -emit-llvm -O1 -mllvm -force-vector-width=2 -o- %s | FileCheck %s --check-prefixes=CHECK,NO-UNROLL
+
+! CHECK-LABEL: @unroll
+! CHECK-SAME: (ptr nocapture writeonly %[[ARG0:.*]])
+subroutine unroll(a)
+  real(kind=8), intent(out) :: a(1000)
+  integer(kind=8) :: i
+    ! CHECK: br label %[[BLK:.*]]
+    ! CHECK: [[BLK]]:
+    ! CHECK-NEXT: %[[IND:.*]] = phi i64 [ 0, %{{.*}} ], [ %[[NIV:.*]], %[[BLK]] ]
+    ! CHECK-NEXT: %[[VIND:.*]] = phi <2 x i64> [ <i64 1, i64 2>, %{{.*}} ], [ %[[NVIND:.*]], %[[BLK]] ]
+    !
+    ! NO-UNROLL-NEXT: %[[IV_D:.*]] = uitofp nneg <2 x i64> %[[VIND]] to <2 x double>
+    ! NO-UNROLL-NEXT: %[[GEP:.*]] = getelementptr double, ptr %[[ARG0]], i64 %[[IND]]
+    ! NO-UNROLL-NEXT: store <2 x double> %[[IV_D]], ptr %[[GEP]]
+    ! NO-UNROLL-NEXT: %[[NIV:.*]] = add nuw i64 %{{.*}}, 2
+    ! NO-UNROLL-NEXT: %[[NVIND]] = add <2 x i64> %[[VIND]], splat (i64 2)
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DavidTruby wrote:

`-funroll-loops` doesn't mean that the loop will be _fully_ unrolled, just that some unrolling can occur. So there's a branch back to the body of the loop in both cases. 

https://github.com/llvm/llvm-project/pull/122906