[llvm] r309444 - [SimplifyCFG] Make the no-jump-tables attribute also disable switch lookup tables

[Sumanth Gundapaneni via llvm-commits]

Author: sgundapa
Date: Fri Jul 28 15:25:40 2017
New Revision: 309444

URL: http://llvm.org/viewvc/llvm-project?rev=309444&view=rev
Log:
[SimplifyCFG] Make the no-jump-tables attribute also disable switch lookup tables

Differential Revision: https://reviews.llvm.org/D35579

Added:
    llvm/trunk/test/Transforms/SimplifyCFG/Hexagon/disable-lookup-table.ll
    llvm/trunk/test/Transforms/SimplifyCFG/disable-lookup-table.ll
Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=309444&r1=309443&r2=309444&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Fri Jul 28 15:25:40 2017
@@ -5151,8 +5151,11 @@ static bool SwitchToLookupTable(SwitchIn
                                 const TargetTransformInfo &TTI) {
   assert(SI->getNumCases() > 1 && "Degenerate switch?");
 
-  // Only build lookup table when we have a target that supports it.
-  if (!TTI.shouldBuildLookupTables())
+  Function *Fn = SI->getParent()->getParent();
+  // Only build lookup table when we have a target that supports it or the
+  // attribute is not set.
+  if (!TTI.shouldBuildLookupTables() ||
+      (Fn->getFnAttribute("no-jump-tables").getValueAsString() == "true"))
     return false;
 
   // FIXME: If the switch is too sparse for a lookup table, perhaps we could
@@ -5333,7 +5336,7 @@ static bool SwitchToLookupTable(SwitchIn
 
     // If using a bitmask, use any value to fill the lookup table holes.
     Constant *DV = NeedMask ? ResultLists[PHI][0].second : DefaultResults[PHI];
-    StringRef FuncName = SI->getParent()->getParent()->getName();
+    StringRef FuncName = Fn->getName();
     SwitchLookupTable Table(Mod, TableSize, MinCaseVal, ResultList, DV, DL,
                             FuncName);
 

Added: llvm/trunk/test/Transforms/SimplifyCFG/Hexagon/disable-lookup-table.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/Hexagon/disable-lookup-table.ll?rev=309444&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/Hexagon/disable-lookup-table.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/Hexagon/disable-lookup-table.ll Fri Jul 28 15:25:40 2017
@@ -0,0 +1,36 @@
+; RUN: opt -S -O2 < %s | FileCheck %s -check-prefix=DISABLE
+; RUN: opt -S -hexagon-emit-lookup-tables=true -O2 < %s | FileCheck %s -check-prefix=DISABLE
+; RUN: opt -S -hexagon-emit-lookup-tables=false -O2 < %s | FileCheck %s -check-prefix=DISABLE
+; The attribute "no-jump-tables"="true" disables the generation of switch generated lookup tables
+
+; DISABLE-NOT: @{{.*}} = private unnamed_addr constant [6 x i32] [i32 9, i32 20, i32 14, i32 22, i32 12, i32 5]
+
+target datalayout = "e-m:e-p:32:32:32-a:0-n16:32-i64:64:64-i32:32:32-i16:16:16-i1:8:8-f32:32:32-f64:64:64-v32:32:32-v64:64:64-v512:512:512-v1024:1024:1024-v2048:2048:2048"
+target triple = "hexagon-unknown--elf"
+
+; Function Attrs: noinline nounwind
+define i32 @foo(i32 %c) #0 {
+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
+}
+
+attributes #0 = { noinline nounwind "no-jump-tables"="true"}

Added: llvm/trunk/test/Transforms/SimplifyCFG/disable-lookup-table.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/disable-lookup-table.ll?rev=309444&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/disable-lookup-table.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/disable-lookup-table.ll Fri Jul 28 15:25:40 2017
@@ -0,0 +1,44 @@
+; RUN: opt < %s -latesimplifycfg -S -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+; In the presence of "-no-jump-tables"="true", late simplifycfg should not
+; convert any switch cases to lookup tables.
+; CHECK: @switch.table.bar = private unnamed_addr constant [4 x i32] [i32 55, i32 123, i32 0, i32 -1]
+; CHECK-LABEL: foo
+; CHECK-NOT: @switch.table.foo = private unnamed_addr constant [4 x i32] [i32 55, i32 123, i32 0, i32 -1]
+
+define i32 @foo(i32 %c) "no-jump-tables"="true" {
+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
+  ]
+
+sw.bb1: br label %return
+sw.bb2: br label %return
+sw.bb3: br label %return
+sw.default: br label %return
+return:
+  %retval.0 = phi i32 [ 15, %sw.default ],  [ -1, %sw.bb3 ], [ 0, %sw.bb2 ], [ 123, %sw.bb1 ], [ 55, %entry ]
+  ret i32 %retval.0
+}
+
+
+define i32 @bar(i32 %c) {
+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
+  ]
+
+sw.bb1: br label %return
+sw.bb2: br label %return
+sw.bb3: br label %return
+sw.default: br label %return
+return:
+  %retval.0 = phi i32 [ 15, %sw.default ],  [ -1, %sw.bb3 ], [ 0, %sw.bb2 ], [ 123, %sw.bb1 ], [ 55, %entry ]
+  ret i32 %retval.0
+}
+