Mark sdivs as 'exact' instead of lowering them ourselves

LLVM's instcombine already translates power-of-two sdivs that are known to be
exact to fast ashr instructions. Hence, there is no need to add this logic
ourselves.

Pointed-out-by: Johannes Doerfert
llvm-svn: 239025
diff --git a/polly/test/Isl/CodeGen/exprModDiv.ll b/polly/test/Isl/CodeGen/exprModDiv.ll
index f3f8b9e..f77013a 100644
--- a/polly/test/Isl/CodeGen/exprModDiv.ll
+++ b/polly/test/Isl/CodeGen/exprModDiv.ll
@@ -42,7 +42,7 @@
 ; CHECK:  %polly.access.A10 = getelementptr float, float* %A, i64 %24
 
 ; A[p / 127]
-; CHECK:  %pexp.div = sdiv i64 %p, 127
+; CHECK:  %pexp.div = sdiv exact i64 %p, 127
 ; CHECK:  %polly.access.B12 = getelementptr float, float* %B, i64 %pexp.div
 
 ; A[i % 128]
@@ -64,8 +64,8 @@
 ; POW2:  %polly.access.A10 = getelementptr float, float* %A, i64 %24
 
 ; A[p / 128]
-; POW2:  %pexp.div.shr = ashr i64 %p, 7
-; POW2:  %polly.access.B12 = getelementptr float, float* %B, i64 %pexp.div.shr
+; POW2:  %pexp.div = sdiv exact i64 %p, 128
+; POW2:  %polly.access.B12 = getelementptr float, float* %B, i64 %pexp.div
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"