[SimplifyCFG] Don't create unnecessary PHIs

In conditional store merging, we were creating PHIs when we didn't
need to. If the value to be predicated isn't defined in the block
we're predicating, then it doesn't need a PHI at all (because we only
deal with triangles and diamonds, any value not in the predicated BB
must dominate the predicated BB).

This fixes a large code size increase in some benchmarks in a popular embedded benchmark suite.

Now with a fix (and fixed tests) for the conformance issue seen in Chromium.

llvm-svn: 255767

1 files changed, 215 insertions, 0 deletions

diff --git a/llvm/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll b/llvm/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
new file mode 100644
index 00000000000..fe498b5334e
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
@@ -0,0 +1,215 @@
+; RUN: opt -S < %s -simplifycfg -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=2 | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7--linux-gnueabihf"
+
+; This is a bit reversal that has been run through the early optimizer (-mem2reg -gvn -instcombine).
+; There should be no additional PHIs created at all. The store should be on its own in a predicated
+; block and there should be no PHIs.
+
+; CHECK-LABEL: @f
+; Exactly 15 phis, as there are 15 in the original test case.
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK: select
+; CHECK-NOT: select
+; CHECK: br i1 {{.*}}, label %[[L:.*]], label %[[R:.*]]
+; CHECK: [[L]] ; preds = 
+; CHECK-NEXT: store
+; CHECK-NEXT: br label %[[R]]
+; CHECK: [[R]] ; preds = 
+; CHECK-NEXT: ret i32 0
+
+define i32 @f(i32* %b) {
+entry:
+  %0 = load i32, i32* %b, align 4
+  %and = and i32 %0, 1
+  %tobool = icmp eq i32 %and, 0
+  br i1 %tobool, label %if.end, label %if.then
+
+if.then:                                          ; preds = %entry
+  %or = or i32 %0, -2147483648
+  store i32 %or, i32* %b, align 4
+  br label %if.end
+
+if.end:                                           ; preds = %entry, %if.then
+  %1 = phi i32 [ %0, %entry ], [ %or, %if.then ]
+  %and1 = and i32 %1, 2
+  %tobool2 = icmp eq i32 %and1, 0
+  br i1 %tobool2, label %if.end5, label %if.then3
+
+if.then3:                                         ; preds = %if.end
+  %or4 = or i32 %1, 1073741824
+  store i32 %or4, i32* %b, align 4
+  br label %if.end5
+
+if.end5:                                          ; preds = %if.end, %if.then3
+  %2 = phi i32 [ %1, %if.end ], [ %or4, %if.then3 ]
+  %and6 = and i32 %2, 4
+  %tobool7 = icmp eq i32 %and6, 0
+  br i1 %tobool7, label %if.end10, label %if.then8
+
+if.then8:                                         ; preds = %if.end5
+  %or9 = or i32 %2, 536870912
+  store i32 %or9, i32* %b, align 4
+  br label %if.end10
+
+if.end10:                                         ; preds = %if.end5, %if.then8
+  %3 = phi i32 [ %2, %if.end5 ], [ %or9, %if.then8 ]
+  %and11 = and i32 %3, 8
+  %tobool12 = icmp eq i32 %and11, 0
+  br i1 %tobool12, label %if.end15, label %if.then13
+
+if.then13:                                        ; preds = %if.end10
+  %or14 = or i32 %3, 268435456
+  store i32 %or14, i32* %b, align 4
+  br label %if.end15
+
+if.end15:                                         ; preds = %if.end10, %if.then13
+  %4 = phi i32 [ %3, %if.end10 ], [ %or14, %if.then13 ]
+  %and16 = and i32 %4, 16
+  %tobool17 = icmp eq i32 %and16, 0
+  br i1 %tobool17, label %if.end20, label %if.then18
+
+if.then18:                                        ; preds = %if.end15
+  %or19 = or i32 %4, 134217728
+  store i32 %or19, i32* %b, align 4
+  br label %if.end20
+
+if.end20:                                         ; preds = %if.end15, %if.then18
+  %5 = phi i32 [ %4, %if.end15 ], [ %or19, %if.then18 ]
+  %and21 = and i32 %5, 32
+  %tobool22 = icmp eq i32 %and21, 0
+  br i1 %tobool22, label %if.end25, label %if.then23
+
+if.then23:                                        ; preds = %if.end20
+  %or24 = or i32 %5, 67108864
+  store i32 %or24, i32* %b, align 4
+  br label %if.end25
+
+if.end25:                                         ; preds = %if.end20, %if.then23
+  %6 = phi i32 [ %5, %if.end20 ], [ %or24, %if.then23 ]
+  %and26 = and i32 %6, 64
+  %tobool27 = icmp eq i32 %and26, 0
+  br i1 %tobool27, label %if.end30, label %if.then28
+
+if.then28:                                        ; preds = %if.end25
+  %or29 = or i32 %6, 33554432
+  store i32 %or29, i32* %b, align 4
+  br label %if.end30
+
+if.end30:                                         ; preds = %if.end25, %if.then28
+  %7 = phi i32 [ %6, %if.end25 ], [ %or29, %if.then28 ]
+  %and31 = and i32 %7, 256
+  %tobool32 = icmp eq i32 %and31, 0
+  br i1 %tobool32, label %if.end35, label %if.then33
+
+if.then33:                                        ; preds = %if.end30
+  %or34 = or i32 %7, 8388608
+  store i32 %or34, i32* %b, align 4
+  br label %if.end35
+
+if.end35:                                         ; preds = %if.end30, %if.then33
+  %8 = phi i32 [ %7, %if.end30 ], [ %or34, %if.then33 ]
+  %and36 = and i32 %8, 512
+  %tobool37 = icmp eq i32 %and36, 0
+  br i1 %tobool37, label %if.end40, label %if.then38
+
+if.then38:                                        ; preds = %if.end35
+  %or39 = or i32 %8, 4194304
+  store i32 %or39, i32* %b, align 4
+  br label %if.end40
+
+if.end40:                                         ; preds = %if.end35, %if.then38
+  %9 = phi i32 [ %8, %if.end35 ], [ %or39, %if.then38 ]
+  %and41 = and i32 %9, 1024
+  %tobool42 = icmp eq i32 %and41, 0
+  br i1 %tobool42, label %if.end45, label %if.then43
+
+if.then43:                                        ; preds = %if.end40
+  %or44 = or i32 %9, 2097152
+  store i32 %or44, i32* %b, align 4
+  br label %if.end45
+
+if.end45:                                         ; preds = %if.end40, %if.then43
+  %10 = phi i32 [ %9, %if.end40 ], [ %or44, %if.then43 ]
+  %and46 = and i32 %10, 2048
+  %tobool47 = icmp eq i32 %and46, 0
+  br i1 %tobool47, label %if.end50, label %if.then48
+
+if.then48:                                        ; preds = %if.end45
+  %or49 = or i32 %10, 1048576
+  store i32 %or49, i32* %b, align 4
+  br label %if.end50
+
+if.end50:                                         ; preds = %if.end45, %if.then48
+  %11 = phi i32 [ %10, %if.end45 ], [ %or49, %if.then48 ]
+  %and51 = and i32 %11, 4096
+  %tobool52 = icmp eq i32 %and51, 0
+  br i1 %tobool52, label %if.end55, label %if.then53
+
+if.then53:                                        ; preds = %if.end50
+  %or54 = or i32 %11, 524288
+  store i32 %or54, i32* %b, align 4
+  br label %if.end55
+
+if.end55:                                         ; preds = %if.end50, %if.then53
+  %12 = phi i32 [ %11, %if.end50 ], [ %or54, %if.then53 ]
+  %and56 = and i32 %12, 8192
+  %tobool57 = icmp eq i32 %and56, 0
+  br i1 %tobool57, label %if.end60, label %if.then58
+
+if.then58:                                        ; preds = %if.end55
+  %or59 = or i32 %12, 262144
+  store i32 %or59, i32* %b, align 4
+  br label %if.end60
+
+if.end60:                                         ; preds = %if.end55, %if.then58
+  %13 = phi i32 [ %12, %if.end55 ], [ %or59, %if.then58 ]
+  %and61 = and i32 %13, 16384
+  %tobool62 = icmp eq i32 %and61, 0
+  br i1 %tobool62, label %if.end65, label %if.then63
+
+if.then63:                                        ; preds = %if.end60
+  %or64 = or i32 %13, 131072
+  store i32 %or64, i32* %b, align 4
+  br label %if.end65
+
+if.end65:                                         ; preds = %if.end60, %if.then63
+  %14 = phi i32 [ %13, %if.end60 ], [ %or64, %if.then63 ]
+  %and66 = and i32 %14, 32768
+  %tobool67 = icmp eq i32 %and66, 0
+  br i1 %tobool67, label %if.end70, label %if.then68
+
+if.then68:                                        ; preds = %if.end65
+  %or69 = or i32 %14, 65536
+  store i32 %or69, i32* %b, align 4
+  br label %if.end70
+
+if.end70:                                         ; preds = %if.end65, %if.then68
+  %15 = phi i32 [ %14, %if.end65 ], [ %or69, %if.then68 ]
+  %and71 = and i32 %15, 128
+  %tobool72 = icmp eq i32 %and71, 0
+  br i1 %tobool72, label %if.end75, label %if.then73
+
+if.then73:                                        ; preds = %if.end70
+  %or74 = or i32 %15, 16777216
+  store i32 %or74, i32* %b, align 4
+  br label %if.end75
+
+if.end75:                                         ; preds = %if.end70, %if.then73
+  ret i32 0
+}