[SimplifyIndvar] Replace the srem used by IV if we can prove both of its operands are non-negative

Since now SCEV can handle 'urem', an 'urem' is a better canonical form than an 'srem' because it has well-defined behavior

This is a follow up of D34598

Differential Revision: https://reviews.llvm.org/D38072

llvm-svn: 314125

2 files changed, 112 insertions, 3 deletions

diff --git a/llvm/test/Transforms/IndVarSimplify/eliminate-rem.ll b/llvm/test/Transforms/IndVarSimplify/eliminate-rem.ll
index 6f8e6bbac77..8c1ea81263f 100644
--- a/llvm/test/Transforms/IndVarSimplify/eliminate-rem.ll
+++ b/llvm/test/Transforms/IndVarSimplify/eliminate-rem.ll
@@ -33,9 +33,9 @@ bb12:                                             ; preds = %bb11, %bb
 
 ; Indvars should be able to eliminate the (i+1)%n.
 ; CHECK-LABEL: @f(
-; CHECK-NOT: rem
-; CHECK: rem
-; CHECK-NOT: rem
+; CHECK-NOT: {{[us]}}rem
+; CHECK: {{[us]}}rem
+; CHECK-NOT: {{[us]}}rem
 ; CHECK: ret
 
 define i32 @f(i64* %arg, i64 %arg1, i64 %arg2, i64 %arg3) nounwind {
diff --git a/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll b/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
new file mode 100644
index 00000000000..6629420df55
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/replace-srem-by-urem.ll
@@ -0,0 +1,109 @@
+; RUN: opt < %s -indvars -S | FileCheck %s
+
+define void @test0(i32* %a) {
+; CHECK-LABEL: @test0(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %rem = srem i32 %i.01, 2
+; CHECK-NOT: srem
+; CHECK:     urem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test2(i32* %a, i32 %d) {
+; CHECK-LABEL: @test2(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %mul = mul nsw i32 %i.01, 64
+  %rem = srem i32 %mul, %d
+; CHECK-NOT: urem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test3(i32* %a) {
+; CHECK-LABEL: @test3(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %rem = srem i32 2048, %i.01
+; CHECK:     urem
+; CHECK-NOT: srem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test4(i32* %a) {
+; CHECK-LABEL: @test4(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %mul = mul nsw i32 %i.01, 64
+  %rem = srem i32 %mul, 8
+; CHECK:     urem
+; CHECK-NOT: srem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+
+define void @test5(i32* %a) {
+; CHECK-LABEL: @test5(
+entry:
+  br label %for.body
+
+for.body:                                         ; preds = %entry, %for.body
+  %i.01 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %mul = mul nsw i32 %i.01, 64
+  %rem = srem i32 %mul, 6
+; CHECK:     urem
+; CHECK-NOT: srem
+  %idxprom = sext i32 %rem to i64
+  %arrayidx = getelementptr inbounds i32, i32* %a, i64 %idxprom
+  store i32 %i.01, i32* %arrayidx, align 4
+  %inc = add nsw i32 %i.01, 1
+  %cmp = icmp slt i32 %inc, 64
+  br i1 %cmp, label %for.body, label %for.end
+
+for.end:                                          ; preds = %for.body
+  ret void
+}
+