[SCEV] Preserve NSW information for sext(subtract).
Pushes the sext onto the operands of a Sub if NSW is present.
Also adds support for propagating the nowrap flags of the
llvm.ssub.with.overflow intrinsic during analysis.
Differential Revision: https://reviews.llvm.org/D35256
llvm-svn: 310117
diff --git a/llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll b/llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll
index 15c679a..8733a85 100644
--- a/llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll
+++ b/llvm/test/Analysis/ScalarEvolution/flags-from-poison.ll
@@ -609,7 +609,7 @@
%index32 = sub nsw i32 %i, %sub
; CHECK: %index64 =
-; CHECK: --> {(sext i32 (-1 * %sub) to i64),+,1}<nsw>
+; CHECK: --> {(-1 * (sext i32 %sub to i64))<nsw>,+,1}<nsw
%index64 = sext i32 %index32 to i64
%ptr = getelementptr inbounds float, float* %input, i64 %index64
@@ -621,6 +621,40 @@
ret void
}
+; Example checking that a sext is pushed onto a sub's operands if the sub is an
+; overflow intrinsic.
+define void @test-sext-sub(float* %input, i32 %sub, i32 %numIterations) {
+; CHECK-LABEL: @test-sext-sub
+entry:
+ br label %loop
+loop:
+ %i = phi i32 [ %nexti, %cont ], [ 0, %entry ]
+
+; CHECK: %val = extractvalue { i32, i1 } %ssub, 0
+; CHECK: --> {(-1 * %sub),+,1}<nw>
+ %ssub = tail call { i32, i1 } @llvm.ssub.with.overflow.i32(i32 %i, i32 %sub)
+ %val = extractvalue { i32, i1 } %ssub, 0
+ %ovfl = extractvalue { i32, i1 } %ssub, 1
+ br i1 %ovfl, label %trap, label %cont
+
+trap:
+ tail call void @llvm.trap()
+ unreachable
+
+cont:
+; CHECK: %index64 =
+; CHECK: --> {(-1 * (sext i32 %sub to i64))<nsw>,+,1}<nsw
+ %index64 = sext i32 %val to i64
+
+ %ptr = getelementptr inbounds float, float* %input, i64 %index64
+ %nexti = add nsw i32 %i, 1
+ %f = load float, float* %ptr, align 4
+ %exitcond = icmp eq i32 %nexti, %numIterations
+ br i1 %exitcond, label %exit, label %loop
+exit:
+ ret void
+}
+
; Two adds with a sub in the middle and the sub should have nsw. There is
; a special case for sequential adds/subs and this test covers that. We have to
; put the final add first in the program since otherwise the special case