Make LoopSimplify change conditional branches in loop exiting blocks

which branch on undef to branch on a boolean constant for the edge
exiting the loop. This helps ScalarEvolution compute trip counts for
loops.

Teach ScalarEvolution to recognize single-value PHIs, when safe, and
ForgetSymbolicName to forget such single-value PHI nodes as apprpriate
in ForgetSymbolicName.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@97126 91177308-0d34-0410-b5e6-96231b3b80d8

3 files changed, 67 insertions, 3 deletions

diff --git a/test/CodeGen/X86/2009-09-07-CoalescerBug.ll b/test/CodeGen/X86/2009-09-07-CoalescerBug.ll
index a5b4a79401..41b4bc0872 100644
--- a/test/CodeGen/X86/2009-09-07-CoalescerBug.ll
+++ b/test/CodeGen/X86/2009-09-07-CoalescerBug.ll
@@ -8,8 +8,7 @@
 define i64 @hammer_time(i64 %modulep, i64 %physfree) nounwind ssp noredzone noimplicitfloat {
 ; CHECK: hammer_time:
 ; CHECK: movq $Xrsvd, %rax
-; CHECK: movq $Xrsvd, %rsi
-; CHECK: movq $Xrsvd, %rdi
+; CHECK: movq $Xrsvd, %rcx
 entry:
   br i1 undef, label %if.then, label %if.end
 
diff --git a/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll b/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
index 30d9ea6fb3..ecd5086f73 100644
--- a/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
+++ b/test/Transforms/IndVarSimplify/2003-09-12-MultiplePred.ll
@@ -7,7 +7,7 @@ define i32 @test() {
 LoopHead:               ; preds = %LoopHead, %0, %0
         %A = phi i32 [ 7, %0 ], [ 7, %0 ], [ %B, %LoopHead ]            ; <i32> [#uses=1]
         %B = add i32 %A, 1              ; <i32> [#uses=2]
-        br i1 undef, label %LoopHead, label %Out
+        br i1 true, label %LoopHead, label %Out
 
 Out:            ; preds = %LoopHead
         ret i32 %B
diff --git a/test/Transforms/LoopDeletion/simplify-then-delete.ll b/test/Transforms/LoopDeletion/simplify-then-delete.ll
new file mode 100644
index 0000000000..5a21672a59
--- /dev/null
+++ b/test/Transforms/LoopDeletion/simplify-then-delete.ll
@@ -0,0 +1,65 @@
+; RUN: opt < %s -S -indvars -loop-deletion -simplifycfg | FileCheck %s
+; PR5794
+
+; Indvars and loop deletion should be able to eliminate all looping
+; in this testcase.
+
+; CHECK:      define i32 @pmat(i32 %m, i32 %n, double* %y) nounwind {
+; CHECK-NEXT: entry:
+; CHECK-NEXT:   ret i32 0
+; CHECK-NEXT: }
+
+target datalayout = "e-p:64:64:64"
+
+define i32 @pmat(i32 %m, i32 %n, double* %y) nounwind {
+entry:
+  %cmp4 = icmp sgt i32 %m, 0
+  br i1 %cmp4, label %bb.n10, label %w.e12
+
+w.c:
+  %cmp = icmp slt i32 %inc11, %m
+  br i1 %cmp, label %w.c2.p, label %w.c.w.e12c
+
+w.c.w.e12c:
+  br label %w.c.w.e12c.s
+
+w.c.w.e12c.s:
+  br label %w.e12
+
+bb.n10:
+  %cmp51 = icmp sgt i32 %n, 0
+  br i1 %cmp51, label %bb.n10.w.c.w.e12c.sc, label %bb.n10.bb.n10.sc
+
+bb.n10.bb.n10.sc:
+  br label %bb.n10.s
+
+bb.n10.w.c.w.e12c.sc:
+  br label %w.c.w.e12c.s
+
+bb.n10.s:
+  br label %w.c2.p
+
+w.c2.p:
+  %i.05 = phi i32 [ 0, %bb.n10.s ], [ %inc11, %w.c ]
+  br i1 false, label %bb.n, label %w.e
+
+w.c2:
+  br i1 undef, label %w.b6, label %w.c2.w.ec
+
+w.c2.w.ec:
+  br label %w.e
+
+bb.n:
+  br label %w.b6
+
+w.b6:
+  br label %w.c2
+
+w.e:
+  %i.08 = phi i32 [ undef, %w.c2.w.ec ], [ %i.05, %w.c2.p ]
+  %inc11 = add nsw i32 %i.08, 1
+  br label %w.c
+
+w.e12:
+  ret i32 0
+}