[PATCH] [ARM] Keep track of previous changes to the bit pattern stored HW_FP

[Ranjeet Singh]

Variable HW_FP could get the wrong bit pattern based on how features are ordered in the Features vector.  If a target had features '+neon' and '+fp-armv8' and the order of these features is ['+fp-armv8', '+neon'] then in the first iteration of the loop HW_FP would be set to the bit pattern  'HW_FP_SP | HW_FP_DP | HW_FP_HP' in the second iteration the value stored in HW_FP would be overwritten with 'HW_FP_SP | HW_FP_DP' and we would loose the bit HW_FP_HP from the previous iteration. The order of the features in the vector shouldn't change the final value in HW_FP.

http://reviews.llvm.org/D10395

Files:
  lib/Basic/Targets.cpp

Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -4239,26 +4239,29 @@
     SoftFloat = SoftFloatABI = false;
     HWDiv = 0;
 
+    // This does not diagnose illegal cases like having both
+    // "+vfpv2" and "+vfpv3" or having "+neon" and "+fp-only-sp".
+    uint32_t HW_FP_remove = 0;
     for (const auto &Feature : Features) {
       if (Feature == "+soft-float") {
         SoftFloat = true;
       } else if (Feature == "+soft-float-abi") {
         SoftFloatABI = true;
       } else if (Feature == "+vfp2") {
         FPU |= VFP2FPU;
-        HW_FP = HW_FP_SP | HW_FP_DP;
+        HW_FP |= HW_FP_SP | HW_FP_DP;
       } else if (Feature == "+vfp3") {
         FPU |= VFP3FPU;
-        HW_FP = HW_FP_SP | HW_FP_DP;
+        HW_FP |= HW_FP_SP | HW_FP_DP;
       } else if (Feature == "+vfp4") {
         FPU |= VFP4FPU;
-        HW_FP = HW_FP_SP | HW_FP_DP | HW_FP_HP;
+        HW_FP |= HW_FP_SP | HW_FP_DP | HW_FP_HP;
       } else if (Feature == "+fp-armv8") {
         FPU |= FPARMV8;
-        HW_FP = HW_FP_SP | HW_FP_DP | HW_FP_HP;
+        HW_FP |= HW_FP_SP | HW_FP_DP | HW_FP_HP;
       } else if (Feature == "+neon") {
         FPU |= NeonFPU;
-        HW_FP = HW_FP_SP | HW_FP_DP;
+        HW_FP |= HW_FP_SP | HW_FP_DP;
       } else if (Feature == "+hwdiv") {
         HWDiv |= HWDivThumb;
       } else if (Feature == "+hwdiv-arm") {
@@ -4268,9 +4271,10 @@
       } else if (Feature == "+crypto") {
         Crypto = 1;
       } else if (Feature == "+fp-only-sp") {
-        HW_FP &= ~HW_FP_DP;
+        HW_FP_remove = HW_FP_DP | HW_FP_HP;
       }
     }
+    HW_FP &= ~HW_FP_remove;
 
     if (!(FPU & NeonFPU) && FPMath == FP_Neon) {
       Diags.Report(diag::err_target_unsupported_fpmath) << "neon";

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