From: Dan Gohman <gohman@apple.com>
Date: Tue, 21 Apr 2009 20:18:36 +0000 (+0000)
Subject: When turning (ashr(shl(x, n), n)) into sext(trunc(x)), the width of the
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=578ccf81e5b94965e3ce8b4eadb6834e39f5f41d;p=oota-llvm.git

When turning (ashr(shl(x, n), n)) into sext(trunc(x)), the width of the
type to truncate to should be the number of bits of the value that are
preserved, not the number that are clobbered with sign-extension.
This fixes regressions in ldecod.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@69704 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp
index ace063a399c..0aa673f355e 100644
--- a/lib/Analysis/ScalarEvolution.cpp
+++ b/lib/Analysis/ScalarEvolution.cpp
@@ -2015,7 +2015,7 @@ SCEVHandle ScalarEvolutionsImpl::createSCEV(Value *V) {
       if (Instruction *L = dyn_cast<Instruction>(U->getOperand(0)))
         if (L->getOpcode() == Instruction::Shl &&
             L->getOperand(1) == U->getOperand(1)) {
-          uint64_t Amt = CI->getZExtValue();
+          uint64_t Amt = getTypeSizeInBits(U->getType()) - CI->getZExtValue();
           return
             SE.getSignExtendExpr(SE.getTruncateExpr(getSCEV(L->getOperand(0)),
                                                     IntegerType::get(Amt)),
diff --git a/test/Analysis/ScalarEvolution/sext-inreg.ll b/test/Analysis/ScalarEvolution/sext-inreg.ll
new file mode 100644
index 00000000000..c482fe6cf57
--- /dev/null
+++ b/test/Analysis/ScalarEvolution/sext-inreg.ll
@@ -0,0 +1,29 @@
+; RUN: llvm-as < %s | opt -analyze -scalar-evolution -disable-output \
+; RUN:  | grep {signextend \{0,+,199\}<bb> to i64} | count 2
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin9.6"
+
+define i64 @foo(i64* nocapture %x, i64 %n) nounwind {
+entry:
+	%t0 = icmp sgt i64 %n, 0		; <i1> [#uses=1]
+	br i1 %t0, label %bb, label %return
+
+bb:		; preds = %bb, %entry
+	%i.01 = phi i64 [ 0, %entry ], [ %indvar.next, %bb ]		; <i32> [#uses=2]
+	%t1 = shl i64 %i.01, 7		; <i32> [#uses=1]
+	%t2 = ashr i64 %t1, 7		; <i32> [#uses=1]
+	%s1 = shl i64 %i.01, 5		; <i32> [#uses=1]
+	%s2 = ashr i64 %s1, 5		; <i32> [#uses=1]
+	%t3 = getelementptr i64* %x, i64 %i.01		; <i64*> [#uses=1]
+	store i64 0, i64* %t3, align 1
+	%indvar.next = add i64 %i.01, 199		; <i32> [#uses=2]
+	%exitcond = icmp eq i64 %indvar.next, %n		; <i1> [#uses=1]
+	br i1 %exitcond, label %return, label %bb
+
+return:		; preds = %bb, %entry
+        %p = phi i64 [ 0, %entry ], [ %t2, %bb ]
+        %q = phi i64 [ 0, %entry ], [ %s2, %bb ]
+        %v = xor i64 %p, %q
+	ret i64 %v
+}