Use TargetTransformInfo to control switch-to-lookup table transformation

When the switch-to-lookup tables transform landed in SimplifyCFG, it
was pointed out that this could be inappropriate for some targets.
Since there was no way at the time for the pass to know anything about
the target, an awkward reverse-transform was added in CodeGenPrepare
that turned lookup tables back into switches for some targets.

This patch uses the new TargetTransformInfo to determine if a
switch should be transformed, and removes
CodeGenPrepare::ConvertLoadToSwitch.

llvm-svn: 167011

3 files changed, 38 insertions, 84 deletions

diff --git a/llvm/test/CodeGen/SPARC/load_to_switch.ll b/llvm/test/CodeGen/SPARC/load_to_switch.ll
deleted file mode 100644
index 8d62de527e4..00000000000
--- a/llvm/test/CodeGen/SPARC/load_to_switch.ll
+++ /dev/null
@@ -1,84 +0,0 @@
-; RUN: llc -march=sparc < %s | FileCheck %s
-
-; Check that all the switches turned into lookup tables by SimplifyCFG are
-; turned back into switches for targets that don't like lookup tables.
-
-@.str = private unnamed_addr constant [4 x i8] c"foo\00", align 1
-@.str1 = private unnamed_addr constant [4 x i8] c"bar\00", align 1
-@.str2 = private unnamed_addr constant [4 x i8] c"baz\00", align 1
-@.str3 = private unnamed_addr constant [4 x i8] c"qux\00", align 1
-@.str4 = private unnamed_addr constant [6 x i8] c"error\00", align 1
-@switch.table = private unnamed_addr constant [7 x i32] [i32 55, i32 123, i32 0, i32 -1, i32 27, i32 62, i32 1]
-@switch.table1 = private unnamed_addr constant [4 x i8] c"*\09X\05"
-@switch.table2 = private unnamed_addr constant [4 x float] [float 0x40091EB860000000, float 0x3FF3BE76C0000000, float 0x4012449BA0000000, float 0x4001AE1480000000]
-@switch.table3 = private unnamed_addr constant [4 x i8*] [i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8]* @.str1, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8]* @.str2, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8]* @.str3, i64 0, i64 0)]
-
-define i32 @f(i32 %c)  {
-entry:
-  %switch.tableidx = sub i32 %c, 42
-  %0 = icmp ult i32 %switch.tableidx, 7
-  br i1 %0, label %switch.lookup, label %return
-
-switch.lookup:
-  %switch.gep = getelementptr inbounds [7 x i32]* @switch.table, i32 0, i32 %switch.tableidx
-  %switch.load = load i32* %switch.gep
-  ret i32 %switch.load
-
-return:
-  ret i32 15
-
-; CHECK: f:
-; CHECK: %switch.lookup
-; CHECK-NOT: sethi %hi(.Lswitch.table)
-}
-
-declare void @dummy(i8 signext, float)
-
-define void @h(i32 %x) {
-entry:
-  %switch.tableidx = sub i32 %x, 0
-  %0 = icmp ult i32 %switch.tableidx, 4
-  br i1 %0, label %switch.lookup, label %sw.epilog
-
-switch.lookup:
-  %switch.gep = getelementptr inbounds [4 x i8]* @switch.table1, i32 0, i32 %switch.tableidx
-  %switch.load = load i8* %switch.gep
-  %switch.gep1 = getelementptr inbounds [4 x float]* @switch.table2, i32 0, i32 %switch.tableidx
-  %switch.load2 = load float* %switch.gep1
-  br label %sw.epilog
-
-sw.epilog:
-  %a.0 = phi i8 [ %switch.load, %switch.lookup ], [ 7, %entry ]
-  %b.0 = phi float [ %switch.load2, %switch.lookup ], [ 0x4023FAE140000000, %entry ]
-  call void @dummy(i8 signext %a.0, float %b.0)
-  ret void
-
-; CHECK: h:
-; CHECK: %switch.lookup
-; CHECK-NOT: sethi %hi(.Lswitch.table{{[0-9]}})
-; CHECK-NOT: sethi %hi(.Lswitch.table{{[0-9]}})
-}
-
-define i8* @foostring(i32 %x) {
-entry:
-  %switch.tableidx = sub i32 %x, 0
-  %0 = icmp ult i32 %switch.tableidx, 4
-  br i1 %0, label %switch.lookup, label %return
-
-switch.lookup:
-  %switch.gep = getelementptr inbounds [4 x i8*]* @switch.table3, i32 0, i32 %switch.tableidx
-  %switch.load = load i8** %switch.gep
-  ret i8* %switch.load
-
-return:
-  ret i8* getelementptr inbounds ([6 x i8]* @.str4, i64 0, i64 0)
-
-; CHECK: foostring:
-; CHECK: %switch.lookup
-; CHECK-NOT: sethi %hi(.Lswitch.table3)
-}
-
-; CHECK-NOT: .Lswitch.table
-; CHECK-NOT: .Lswitch.table1
-; CHECK-NOT: .Lswitch.table2
-; CHECK-NOT: .Lswitch.table3
diff --git a/llvm/test/Transforms/SimplifyCFG/SPARC/lit.local.cfg b/llvm/test/Transforms/SimplifyCFG/SPARC/lit.local.cfg
new file mode 100644
index 00000000000..786fee9e661
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/SPARC/lit.local.cfg
@@ -0,0 +1,6 @@
+config.suffixes = ['.ll', '.c', '.cpp']
+
+targets = set(config.root.targets_to_build.split())
+if not 'Sparc' in targets:
+    config.unsupported = True
+
diff --git a/llvm/test/Transforms/SimplifyCFG/SPARC/switch_to_lookup_table.ll b/llvm/test/Transforms/SimplifyCFG/SPARC/switch_to_lookup_table.ll
new file mode 100644
index 00000000000..9d1568557f3
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/SPARC/switch_to_lookup_table.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -simplifycfg -S -mtriple=sparc-unknown-unknown | FileCheck %s
+
+; Check that switches are not turned into lookup tables, as this is not
+; considered profitable on the target.
+
+define i32 @f(i32 %c) nounwind uwtable readnone {
+entry:
+  switch i32 %c, label %sw.default [
+    i32 42, label %return
+    i32 43, label %sw.bb1
+    i32 44, label %sw.bb2
+    i32 45, label %sw.bb3
+    i32 46, label %sw.bb4
+    i32 47, label %sw.bb5
+    i32 48, label %sw.bb6
+  ]
+
+sw.bb1: br label %return
+sw.bb2: br label %return
+sw.bb3: br label %return
+sw.bb4: br label %return
+sw.bb5: br label %return
+sw.bb6: br label %return
+sw.default: br label %return
+return:
+  %retval.0 = phi i32 [ 15, %sw.default ], [ 1, %sw.bb6 ], [ 62, %sw.bb5 ], [ 27, %sw.bb4 ], [ -1, %sw.bb3 ], [ 0, %sw.bb2 ], [ 123, %sw.bb1 ], [ 55, %entry ]
+  ret i32 %retval.0
+
+; CHECK: @f
+; CHECK-NOT: getelementptr
+; CHECK: switch i32 %c
+}