From: Guozhi Wei <carrot@google.com>
Date: Thu, 14 Sep 2017 19:20:02 +0000 (+0000)
Subject: [TargetTransformInfo] Detect 0 latency instructions
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5cf5798b90e622f8b2db6b9e166bc404082c2c0e;p=llvm

[TargetTransformInfo] Detect 0 latency instructions

For instructions that unlikely generate machine instructions, they should also have 0 latency.

Differential Revision: https://reviews.llvm.org/D37833



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313288 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/llvm/Analysis/TargetTransformInfoImpl.h b/include/llvm/Analysis/TargetTransformInfoImpl.h
index 87d30ef225e..2191bd16456 100644
--- a/include/llvm/Analysis/TargetTransformInfoImpl.h
+++ b/include/llvm/Analysis/TargetTransformInfoImpl.h
@@ -775,7 +775,9 @@ public:
   }
 
   int getInstructionLatency(const Instruction *I) {
-    if (isa<PHINode>(I))
+    SmallVector<const Value *, 4> Operands(I->value_op_begin(),
+                                           I->value_op_end());
+    if (getUserCost(I, Operands) == TTI::TCC_Free)
       return 0;
 
     if (isa<CallInst>(I))
diff --git a/test/Analysis/CostModel/X86/costmodel.ll b/test/Analysis/CostModel/X86/costmodel.ll
index 1b3d784323b..f7958580b13 100644
--- a/test/Analysis/CostModel/X86/costmodel.ll
+++ b/test/Analysis/CostModel/X86/costmodel.ll
@@ -3,6 +3,8 @@
 
 ; Tests if the interface TargetTransformInfo::getInstructionCost() works correctly.
 
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
 define i64 @foo(i64 %arg) {
 
   ; LATENCY:  cost of 1 {{.*}} %I64 = add
@@ -13,6 +15,22 @@ define i64 @foo(i64 %arg) {
   ; CODESIZE: cost of 1 {{.*}} load
   load i64, i64* undef, align 4
 
+  ; LATENCY:  cost of 0 {{.*}} bitcast
+  ; CODESIZE: cost of 0 {{.*}} bitcast
+  %BC = bitcast i8* undef to i32*
+
+  ; LATENCY:  cost of 0 {{.*}} inttoptr
+  ; CODESIZE: cost of 0 {{.*}} inttoptr
+  %I2P = inttoptr i64 undef to i8*
+
+  ; LATENCY:  cost of 0 {{.*}} ptrtoint
+  ; CODESIZE: cost of 0 {{.*}} ptrtoint
+  %P2I = ptrtoint i8* undef to i64
+
+  ; LATENCY:  cost of 0 {{.*}} trunc
+  ; CODESIZE: cost of 0 {{.*}} trunc
+  %TC = trunc i64 undef to i32
+
   ; LATENCY:  cost of 1 {{.*}} ret
   ; CODESIZE: cost of 1 {{.*}} ret
   ret i64 undef