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

[Kiran Chandramohan 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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kiranchandramohan wrote:

For small loops, it will fully unroll if the body is small.

The issue with checking for two iterations is that this could be due to interleaving during vectorisation as well.

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